Index

This module defines the types for the MCP protocol.

Check the latest schema at: https://github.com/modelcontextprotocol/modelcontextprotocol/blob/main/schema/draft/schema.json

CLIENT_CAPABILITIES_META_KEY module-attribute

CLIENT_CAPABILITIES_META_KEY = (
    "io.modelcontextprotocol/clientCapabilities"
)

Reserved request _meta key: per-request ClientCapabilities (2026-07-28). SDK-managed.

CLIENT_INFO_META_KEY module-attribute

CLIENT_INFO_META_KEY = 'io.modelcontextprotocol/clientInfo'

Reserved request _meta key: the client Implementation (2026-07-28). SDK-managed.

DEFAULT_NEGOTIATED_VERSION module-attribute

DEFAULT_NEGOTIATED_VERSION: Final[str] = '2025-03-26'

The default negotiated version of the Model Context Protocol when no version is specified.

We need this to satisfy the MCP specification, which requires the server to assume a specific version if none is provided by the client.

See the "Protocol Version Header" at https://modelcontextprotocol.io/specification/2025-11-25/basic/transports#protocol-version-header.

LOG_LEVEL_META_KEY module-attribute

LOG_LEVEL_META_KEY = 'io.modelcontextprotocol/logLevel'

Reserved request _meta key: desired log level for this request (2026-07-28).

Deprecated (with the rest of logging) by SEP-2577 in the same revision that introduces it. If absent, the server must not send log notifications.

PROTOCOL_VERSION_META_KEY module-attribute

PROTOCOL_VERSION_META_KEY = (
    "io.modelcontextprotocol/protocolVersion"
)

Reserved request _meta key: the MCP protocol version for this request (2026-07-28).

SDK-managed; for HTTP its value must match the MCP-Protocol-Version header.

Annotations

Bases: MCPModel

Optional annotations the client can use to inform how objects are used or displayed.

Source code in src/mcp-types/mcp_types/_types.py

class Annotations(MCPModel):
    """Optional annotations the client can use to inform how objects are used or displayed."""

    audience: list[Role] | None = None
    """Who the intended audience is, e.g. `["user", "assistant"]`."""

    priority: Annotated[float, Field(ge=0.0, le=1.0)] | None = None
    """How important this data is for operating the server: 1 means effectively
    required, 0 means entirely optional."""

    last_modified: str | None = None
    """ISO 8601 timestamp of when the item was last modified."""

audience class-attribute instance-attribute

audience: list[Role] | None = None

Who the intended audience is, e.g. ["user", "assistant"].

priority class-attribute instance-attribute

priority: Annotated[float, Field(ge=0.0, le=1.0)] | None = (
    None
)

How important this data is for operating the server: 1 means effectively required, 0 means entirely optional.

last_modified class-attribute instance-attribute

last_modified: str | None = None

ISO 8601 timestamp of when the item was last modified.

AudioContent

Bases: MCPModel

Audio provided to or from an LLM.

Source code in src/mcp-types/mcp_types/_types.py

class AudioContent(MCPModel):
    """Audio provided to or from an LLM."""

    type: Literal["audio"] = "audio"
    data: str
    """The base64-encoded audio data."""
    mime_type: str
    """
    The MIME type of the audio. Different providers may support different
    audio types.
    """
    annotations: Annotations | None = None
    """Optional annotations for the client."""
    meta: Meta | None = Field(alias="_meta", default=None)
    """
    See [MCP specification](https://github.com/modelcontextprotocol/modelcontextprotocol/blob/47339c03c143bb4ec01a26e721a1b8fe66634ebe/docs/specification/draft/basic/index.mdx#general-fields)
    for notes on _meta usage.
    """

data instance-attribute

data: str

The base64-encoded audio data.

mime_type instance-attribute

mime_type: str

The MIME type of the audio. Different providers may support different audio types.

annotations class-attribute instance-attribute

annotations: Annotations | None = None

Optional annotations for the client.

meta class-attribute instance-attribute

meta: Meta | None = Field(alias='_meta', default=None)

See MCP specification for notes on _meta usage.

BaseMetadata

Bases: MCPModel

Base class for entities with a programmatic name and an optional display title.

Source code in src/mcp-types/mcp_types/_types.py

class BaseMetadata(MCPModel):
    """Base class for entities with a programmatic name and an optional display title."""

    name: str
    """Intended for programmatic or logical use, but used as a display name in past
    specs or fallback (if title isn't present)."""

    title: str | None = None
    """
    Intended for UI and end-user contexts — optimized to be human-readable and easily understood,
    even by those unfamiliar with domain-specific terminology.

    If not provided, the name should be used for display (except for Tool,
    where `annotations.title` should be given precedence over using `name`,
    if present).
    """

name instance-attribute

name: str

Intended for programmatic or logical use, but used as a display name in past specs or fallback (if title isn't present).

title class-attribute instance-attribute

title: str | None = None

Intended for UI and end-user contexts — optimized to be human-readable and easily understood, even by those unfamiliar with domain-specific terminology.

If not provided, the name should be used for display (except for Tool, where annotations.title should be given precedence over using name, if present).

BlobResourceContents

Bases: ResourceContents

Binary contents of a resource.

Source code in src/mcp-types/mcp_types/_types.py

class BlobResourceContents(ResourceContents):
    """Binary contents of a resource."""

    blob: str
    """A base64-encoded string representing the binary data of the item."""

blob instance-attribute

blob: str

A base64-encoded string representing the binary data of the item.

CacheableResult

Bases: Result

Base class for results that carry client-side caching directives (2026-07-28).

Both fields are required on the 2026-07-28 wire. The SDK defaults to ttl_ms=0 (immediately stale) and cache_scope="private" so a handler that doesn't set them still produces a valid 2026-07-28 result without accidentally enabling shared caching.

Source code in src/mcp-types/mcp_types/_types.py

class CacheableResult(Result):
    """Base class for results that carry client-side caching directives (2026-07-28).

    Both fields are required on the 2026-07-28 wire. The SDK defaults to
    `ttl_ms=0` (immediately stale) and `cache_scope="private"` so a handler
    that doesn't set them still produces a valid 2026-07-28 result without
    accidentally enabling shared caching.
    """

    ttl_ms: Annotated[int, Field(ge=0)] = 0
    """How long (ms) the client MAY cache this response, analogous to HTTP
    `Cache-Control: max-age`. 0 means immediately stale."""

    cache_scope: Literal["public", "private"] = "private"
    """Analogous to HTTP `Cache-Control: public` vs `private`: "public" allows
    shared caches to serve the response to any user; "private" forbids that."""

ttl_ms class-attribute instance-attribute

ttl_ms: Annotated[int, Field(ge=0)] = 0

How long (ms) the client MAY cache this response, analogous to HTTP Cache-Control: max-age. 0 means immediately stale.

cache_scope class-attribute instance-attribute

cache_scope: Literal['public', 'private'] = 'private'

Analogous to HTTP Cache-Control: public vs private: "public" allows shared caches to serve the response to any user; "private" forbids that.

CallToolRequest

Bases: Request[CallToolRequestParams, Literal['tools/call']]

Used by the client to invoke a tool provided by the server.

Source code in src/mcp-types/mcp_types/_types.py

class CallToolRequest(Request[CallToolRequestParams, Literal["tools/call"]]):
    """Used by the client to invoke a tool provided by the server."""

    method: Literal["tools/call"] = "tools/call"
    params: CallToolRequestParams

CallToolRequestParams

Bases: InputResponseRequestParams

Source code in src/mcp-types/mcp_types/_types.py

class CallToolRequestParams(InputResponseRequestParams):
    name: str
    arguments: dict[str, Any] | None = None
    task: TaskMetadata | None = None
    """If specified, the caller requests task-augmented execution (2025-11-25 only)."""

task class-attribute instance-attribute

task: TaskMetadata | None = None

If specified, the caller requests task-augmented execution (2025-11-25 only).

CallToolResult

Bases: Result

The server's response to a tool call.

Errors that originate from the tool SHOULD be reported inside the result with is_error set to true, not as an MCP protocol-level error, so the LLM can see and self-correct. Errors in finding the tool, or any other exceptional condition, should be reported as an MCP error response.

Source code in src/mcp-types/mcp_types/_types.py

class CallToolResult(Result):
    """The server's response to a tool call.

    Errors that originate from the tool SHOULD be reported inside the result
    with `is_error` set to true, not as an MCP protocol-level error, so the LLM
    can see and self-correct. Errors in finding the tool, or any other
    exceptional condition, should be reported as an MCP error response.
    """

    content: list[ContentBlock]
    """A list of content objects that represent the unstructured result of the tool call."""
    structured_content: Any = None
    """An optional JSON value representing the structured result of the tool call.

    Any JSON value on 2026-07-28; restricted to a JSON object on 2025-06-18 and
    2025-11-25.
    """
    is_error: bool = False
    """Whether the tool call ended in an error."""

    result_type: ResultType = "complete"
    """See `ResultType`. Always serialized; older peers ignore it."""

content instance-attribute

content: list[ContentBlock]

A list of content objects that represent the unstructured result of the tool call.

structured_content class-attribute instance-attribute

structured_content: Any = None

An optional JSON value representing the structured result of the tool call.

Any JSON value on 2026-07-28; restricted to a JSON object on 2025-06-18 and 2025-11-25.

is_error class-attribute instance-attribute

is_error: bool = False

Whether the tool call ended in an error.

result_type class-attribute instance-attribute

result_type: ResultType = 'complete'

See ResultType. Always serialized; older peers ignore it.

CancelledNotification

Bases: Notification[CancelledNotificationParams, Literal['notifications/cancelled']]

This notification can be sent by either side to indicate that it is canceling a previously-issued request.

The request SHOULD still be in-flight, but due to communication latency, it is always possible that this notification MAY arrive after the request has already finished. A client MUST NOT attempt to cancel its initialize request.

Source code in src/mcp-types/mcp_types/_types.py

class CancelledNotification(Notification[CancelledNotificationParams, Literal["notifications/cancelled"]]):
    """This notification can be sent by either side to indicate that it is canceling a
    previously-issued request.

    The request SHOULD still be in-flight, but due to communication latency, it
    is always possible that this notification MAY arrive after the request has
    already finished. A client MUST NOT attempt to cancel its `initialize` request.
    """

    method: Literal["notifications/cancelled"] = "notifications/cancelled"
    params: CancelledNotificationParams

CancelledNotificationParams

Bases: NotificationParams

Source code in src/mcp-types/mcp_types/_types.py

class CancelledNotificationParams(NotificationParams):
    request_id: RequestId | None = None
    """
    The ID of the request to cancel.

    This MUST correspond to the ID of a request previously issued in the same direction.
    Required on the wire through 2025-06-18; optional at 2025-11-25; required again from
    2026-07-28, where it must name a request the client previously issued (servers send
    this notification only to terminate a `subscriptions/listen` stream).
    """
    reason: str | None = None
    """An optional string describing the reason for the cancellation."""

request_id class-attribute instance-attribute

request_id: RequestId | None = None

The ID of the request to cancel.

This MUST correspond to the ID of a request previously issued in the same direction. Required on the wire through 2025-06-18; optional at 2025-11-25; required again from 2026-07-28, where it must name a request the client previously issued (servers send this notification only to terminate a subscriptions/listen stream).

reason class-attribute instance-attribute

reason: str | None = None

An optional string describing the reason for the cancellation.

CancelTaskRequest

Bases: Request[CancelTaskRequestParams, Literal['tasks/cancel']]

A request to cancel a task (2025-11-25 only).

Source code in src/mcp-types/mcp_types/_types.py

class CancelTaskRequest(Request[CancelTaskRequestParams, Literal["tasks/cancel"]]):
    """A request to cancel a task (2025-11-25 only)."""

    method: Literal["tasks/cancel"] = "tasks/cancel"
    params: CancelTaskRequestParams

CancelTaskResult

Bases: Result, Task

The response to a tasks/cancel request (2025-11-25 only).

Source code in src/mcp-types/mcp_types/_types.py

class CancelTaskResult(Result, Task):
    """The response to a tasks/cancel request (2025-11-25 only)."""

ClientCapabilities

Bases: MCPModel

Capabilities a client may support.

Not a closed set: any client can define additional capabilities. Sent once in initialize through 2025-11-25; per-request in _meta on 2026-07-28.

Source code in src/mcp-types/mcp_types/_types.py

class ClientCapabilities(MCPModel):
    """Capabilities a client may support.

    Not a closed set: any client can define additional capabilities. Sent once in
    `initialize` through 2025-11-25; per-request in `_meta` on 2026-07-28.
    """

    experimental: dict[str, dict[str, Any]] | None = None
    """Experimental, non-standard capabilities that the client supports."""
    sampling: SamplingCapability | None = None
    """
    Present if the client supports sampling from an LLM.
    Can contain fine-grained capabilities like context and tools support.
    """
    elicitation: ElicitationCapability | None = None
    """Present if the client supports elicitation from the user."""
    roots: RootsCapability | None = None
    """Present if the client supports listing roots."""
    extensions: dict[str, dict[str, Any]] | None = None
    """MCP extensions the client supports (2026-07-28). Keys are extension
    identifiers; values are per-extension settings (empty object = no settings)."""
    tasks: ClientTasksCapability | None = None
    """Present if the client supports task-augmented requests (2025-11-25 only)."""

experimental class-attribute instance-attribute

experimental: dict[str, dict[str, Any]] | None = None

Experimental, non-standard capabilities that the client supports.

sampling class-attribute instance-attribute

sampling: SamplingCapability | None = None

Present if the client supports sampling from an LLM. Can contain fine-grained capabilities like context and tools support.

elicitation class-attribute instance-attribute

elicitation: ElicitationCapability | None = None

Present if the client supports elicitation from the user.

roots class-attribute instance-attribute

roots: RootsCapability | None = None

Present if the client supports listing roots.

extensions class-attribute instance-attribute

extensions: dict[str, dict[str, Any]] | None = None

MCP extensions the client supports (2026-07-28). Keys are extension identifiers; values are per-extension settings (empty object = no settings).

tasks class-attribute instance-attribute

tasks: ClientTasksCapability | None = None

Present if the client supports task-augmented requests (2025-11-25 only).

ClientNotification module-attribute

ClientNotification = (
    CancelledNotification
    | ProgressNotification
    | InitializedNotification
    | RootsListChangedNotification
)

Notifications sent from the client to the server.

TaskStatusNotification is deliberately excluded (types-only).

ClientRequest module-attribute

ClientRequest = (
    PingRequest
    | InitializeRequest
    | CompleteRequest
    | SetLevelRequest
    | GetPromptRequest
    | ListPromptsRequest
    | ListResourcesRequest
    | ListResourceTemplatesRequest
    | ReadResourceRequest
    | SubscribeRequest
    | UnsubscribeRequest
    | CallToolRequest
    | ListToolsRequest
    | DiscoverRequest
    | SubscriptionsListenRequest
)

Union of client-to-server request payloads across all supported protocol versions.

The 2025-11-25 task requests are deliberately excluded (types-only).

ClientTasksCapability

Bases: MCPModel

Capability for client tasks operations (2025-11-25 only).

Source code in src/mcp-types/mcp_types/_types.py

class ClientTasksCapability(MCPModel):
    """Capability for client tasks operations (2025-11-25 only)."""

    list: TasksListCapability | None = None
    cancel: TasksCancelCapability | None = None
    requests: ClientTasksRequestsCapability | None = None

ClientTasksRequestsCapability

Bases: MCPModel

Specifies which request types the client can augment with tasks (2025-11-25 only).

Source code in src/mcp-types/mcp_types/_types.py

class ClientTasksRequestsCapability(MCPModel):
    """Specifies which request types the client can augment with tasks (2025-11-25 only)."""

    sampling: TasksSamplingCapability | None = None
    elicitation: TasksElicitationCapability | None = None

CompleteRequest

Bases: Request[CompleteRequestParams, Literal['completion/complete']]

A request from the client to the server, to ask for completion options.

Source code in src/mcp-types/mcp_types/_types.py

class CompleteRequest(Request[CompleteRequestParams, Literal["completion/complete"]]):
    """A request from the client to the server, to ask for completion options."""

    method: Literal["completion/complete"] = "completion/complete"
    params: CompleteRequestParams

CompleteRequestParams

Bases: RequestParams

Source code in src/mcp-types/mcp_types/_types.py

class CompleteRequestParams(RequestParams):
    ref: ResourceTemplateReference | PromptReference
    """The prompt or resource-template reference to complete against."""
    argument: CompletionArgument
    context: CompletionContext | None = None
    """Additional, optional context for completions."""

ref instance-attribute

ref: ResourceTemplateReference | PromptReference

The prompt or resource-template reference to complete against.

context class-attribute instance-attribute

context: CompletionContext | None = None

Additional, optional context for completions.

CompleteResult

Bases: Result

The server's response to a completion/complete request.

Source code in src/mcp-types/mcp_types/_types.py

class CompleteResult(Result):
    """The server's response to a completion/complete request."""

    completion: Completion
    """The completion values, with optional total / has-more pagination hints."""

    result_type: ResultType = "complete"
    """See `ResultType`. Always serialized; older peers ignore it."""

completion instance-attribute

completion: Completion

The completion values, with optional total / has-more pagination hints.

result_type class-attribute instance-attribute

result_type: ResultType = 'complete'

See ResultType. Always serialized; older peers ignore it.

Completion

Bases: MCPModel

Completion information.

Source code in src/mcp-types/mcp_types/_types.py

class Completion(MCPModel):
    """Completion information."""

    values: list[str]
    """An array of completion values. Must not exceed 100 items."""
    total: int | None = None
    """
    The total number of completion options available. This can exceed the number of
    values actually sent in the response.
    """
    has_more: bool | None = None
    """
    Indicates whether there are additional completion options beyond those provided in
    the current response, even if the exact total is unknown.
    """

values instance-attribute

values: list[str]

An array of completion values. Must not exceed 100 items.

total class-attribute instance-attribute

total: int | None = None

The total number of completion options available. This can exceed the number of values actually sent in the response.

has_more class-attribute instance-attribute

has_more: bool | None = None

Indicates whether there are additional completion options beyond those provided in the current response, even if the exact total is unknown.

CompletionArgument

Bases: MCPModel

The argument's information for completion requests.

Source code in src/mcp-types/mcp_types/_types.py

class CompletionArgument(MCPModel):
    """The argument's information for completion requests."""

    name: str
    """The name of the argument."""
    value: str
    """The value of the argument to use for completion matching."""

name instance-attribute

name: str

The name of the argument.

value instance-attribute

value: str

The value of the argument to use for completion matching.

CompletionContext

Bases: MCPModel

Additional, optional context for completions.

Source code in src/mcp-types/mcp_types/_types.py

class CompletionContext(MCPModel):
    """Additional, optional context for completions."""

    arguments: dict[str, str] | None = None
    """Previously-resolved variables in a URI template or prompt."""

arguments class-attribute instance-attribute

arguments: dict[str, str] | None = None

Previously-resolved variables in a URI template or prompt.

CompletionsCapability

Bases: MCPModel

Capability for completions operations.

Source code in src/mcp-types/mcp_types/_types.py

class CompletionsCapability(MCPModel):
    """Capability for completions operations."""

ContentBlock module-attribute

ContentBlock = (
    TextContent
    | ImageContent
    | AudioContent
    | ResourceLink
    | EmbeddedResource
)

A content block that can be used in prompts and tool results.

CreateMessageRequest

Bases: Request[CreateMessageRequestParams, Literal['sampling/createMessage']]

A request from the server to sample an LLM via the client.

The client has full discretion over which model to select and should inform the user before sampling (human in the loop). A standalone JSON-RPC request through 2025-11-25; on 2026-07-28 it is embedded in InputRequiredResult.input_requests instead. Deprecated in 2026-07-28 (SEP-2577).

Source code in src/mcp-types/mcp_types/_types.py

class CreateMessageRequest(Request[CreateMessageRequestParams, Literal["sampling/createMessage"]]):
    """A request from the server to sample an LLM via the client.

    The client has full discretion over which model to select and should inform
    the user before sampling (human in the loop). A standalone JSON-RPC request
    through 2025-11-25; on 2026-07-28 it is embedded in
    `InputRequiredResult.input_requests` instead. Deprecated in 2026-07-28 (SEP-2577).
    """

    method: Literal["sampling/createMessage"] = "sampling/createMessage"
    params: CreateMessageRequestParams

CreateMessageRequestParams

Bases: RequestParams

Source code in src/mcp-types/mcp_types/_types.py

class CreateMessageRequestParams(RequestParams):
    messages: list[SamplingMessage]
    """The conversation to sample from."""
    model_preferences: ModelPreferences | None = None
    """
    The server's preferences for which model to select. The client MAY ignore
    these preferences.
    """
    system_prompt: str | None = None
    """An optional system prompt the server wants to use for sampling."""
    include_context: IncludeContext | None = None
    """
    A request to include context from one or more MCP servers (including the
    caller), to be attached to the prompt. The client MAY ignore this request.
    Default is "none". "thisServer" and "allServers" are deprecated (SEP-2596).
    """
    temperature: float | None = None
    max_tokens: int
    """The maximum number of tokens to sample, as requested by the server."""
    stop_sequences: list[str] | None = None
    metadata: dict[str, Any] | None = None
    """Optional metadata to pass through to the LLM provider. Provider-specific."""
    tools: list[Tool] | None = None
    """Tools the model may use during generation (2025-11-25+). Requires the
    `sampling.tools` client capability."""
    tool_choice: ToolChoice | None = None
    """Controls how the model uses tools (2025-11-25+). Requires the
    `sampling.tools` client capability."""
    task: TaskMetadata | None = None
    """If specified, the caller requests task-augmented execution (2025-11-25 only)."""

messages instance-attribute

messages: list[SamplingMessage]

The conversation to sample from.

model_preferences class-attribute instance-attribute

model_preferences: ModelPreferences | None = None

The server's preferences for which model to select. The client MAY ignore these preferences.

system_prompt class-attribute instance-attribute

system_prompt: str | None = None

An optional system prompt the server wants to use for sampling.

include_context class-attribute instance-attribute

include_context: IncludeContext | None = None

A request to include context from one or more MCP servers (including the caller), to be attached to the prompt. The client MAY ignore this request. Default is "none". "thisServer" and "allServers" are deprecated (SEP-2596).

max_tokens instance-attribute

max_tokens: int

The maximum number of tokens to sample, as requested by the server.

metadata class-attribute instance-attribute

metadata: dict[str, Any] | None = None

Optional metadata to pass through to the LLM provider. Provider-specific.

tools class-attribute instance-attribute

tools: list[Tool] | None = None

Tools the model may use during generation (2025-11-25+). Requires the sampling.tools client capability.

tool_choice class-attribute instance-attribute

tool_choice: ToolChoice | None = None

Controls how the model uses tools (2025-11-25+). Requires the sampling.tools client capability.

task class-attribute instance-attribute

task: TaskMetadata | None = None

If specified, the caller requests task-augmented execution (2025-11-25 only).

CreateMessageResult

Bases: Result

The client's response to a sampling/createMessage request from the server.

This is the backwards-compatible version that returns single content (no arrays). Used when the request does not include tools.

On 2026-07-28 this travels embedded in an InputResponses map rather than as a top-level JSON-RPC result. Deprecated in 2026-07-28 (SEP-2577).

Source code in src/mcp-types/mcp_types/_types.py

class CreateMessageResult(Result):
    """The client's response to a sampling/createMessage request from the server.

    This is the backwards-compatible version that returns single content (no arrays).
    Used when the request does not include tools.

    On 2026-07-28 this travels embedded in an `InputResponses` map rather than
    as a top-level JSON-RPC result. Deprecated in 2026-07-28 (SEP-2577).
    """

    role: Role
    """The role of the message sender (typically 'assistant' for LLM responses)."""
    content: SamplingContent
    """Response content. Single content block (text, image, or audio)."""
    model: str
    """The name of the model that generated the message."""
    stop_reason: StopReason | None = None
    """The reason why sampling stopped, if known."""

role instance-attribute

role: Role

The role of the message sender (typically 'assistant' for LLM responses).

content instance-attribute

content: SamplingContent

Response content. Single content block (text, image, or audio).

model instance-attribute

model: str

The name of the model that generated the message.

stop_reason class-attribute instance-attribute

stop_reason: StopReason | None = None

The reason why sampling stopped, if known.

CreateMessageResultWithTools

Bases: Result

The client's response to a sampling/createMessage request when tools were provided.

This version supports array content for tool use flows (2025-11-25 and later).

Source code in src/mcp-types/mcp_types/_types.py

class CreateMessageResultWithTools(Result):
    """The client's response to a sampling/createMessage request when tools were provided.

    This version supports array content for tool use flows (2025-11-25 and later).
    """

    role: Role
    """The role of the message sender (typically 'assistant' for LLM responses)."""
    content: SamplingMessageContentBlock | list[SamplingMessageContentBlock]
    """
    Response content. May be a single content block or an array.
    May include ToolUseContent if stop_reason is 'toolUse'.
    """
    model: str
    """The name of the model that generated the message."""
    stop_reason: StopReason | None = None
    """
    The reason why sampling stopped, if known.
    'toolUse' indicates the model wants to use a tool.
    """

    @property
    def content_as_list(self) -> list[SamplingMessageContentBlock]:
        """Returns the content as a list of content blocks, regardless of whether
        it was originally a single block or a list."""
        return self.content if isinstance(self.content, list) else [self.content]

role instance-attribute

role: Role

The role of the message sender (typically 'assistant' for LLM responses).

content instance-attribute

content: (
    SamplingMessageContentBlock
    | list[SamplingMessageContentBlock]
)

Response content. May be a single content block or an array. May include ToolUseContent if stop_reason is 'toolUse'.

model instance-attribute

model: str

The name of the model that generated the message.

stop_reason class-attribute instance-attribute

stop_reason: StopReason | None = None

The reason why sampling stopped, if known. 'toolUse' indicates the model wants to use a tool.

content_as_list property

content_as_list: list[SamplingMessageContentBlock]

Returns the content as a list of content blocks, regardless of whether it was originally a single block or a list.

CreateTaskResult

Bases: Result

A response to a task-augmented request (2025-11-25 only).

Source code in src/mcp-types/mcp_types/_types.py

class CreateTaskResult(Result):
    """A response to a task-augmented request (2025-11-25 only)."""

    task: Task

DiscoverRequest

Bases: Request[RequestParams | None, Literal['server/discover']]

Asks the server to advertise its supported protocol versions, capabilities, and other metadata (2026-07-28).

Servers speaking 2026-07-28 MUST implement this; clients MAY call it but are not required to (version negotiation can also happen via per-request _meta).

Source code in src/mcp-types/mcp_types/_types.py

class DiscoverRequest(Request[RequestParams | None, Literal["server/discover"]]):
    """Asks the server to advertise its supported protocol versions, capabilities,
    and other metadata (2026-07-28).

    Servers speaking 2026-07-28 MUST implement this; clients MAY call it but are
    not required to (version negotiation can also happen via per-request `_meta`).
    """

    method: Literal["server/discover"] = "server/discover"
    params: RequestParams | None = None
    """Required on the 2026-07-28 wire (for `_meta`); the session layer materializes it."""

params class-attribute instance-attribute

params: RequestParams | None = None

Required on the 2026-07-28 wire (for _meta); the session layer materializes it.

DiscoverResult

Bases: CacheableResult

The result returned by the server for a server/discover request (2026-07-28).

Source code in src/mcp-types/mcp_types/_types.py

class DiscoverResult(CacheableResult):
    """The result returned by the server for a `server/discover` request (2026-07-28)."""

    supported_versions: list[str]
    """MCP protocol versions this server supports; the client should pick one for subsequent requests."""

    capabilities: ServerCapabilities

    server_info: Implementation

    instructions: str | None = None
    """Natural-language guidance describing the server and its features, e.g. for
    a system prompt. Should not duplicate information already in tool descriptions."""

    result_type: ResultType = "complete"
    """See `ResultType`. Always serialized; required on the 2026-07-28 wire,
    ignored by older peers, and defaulted on inbound bodies that omit it."""

supported_versions instance-attribute

supported_versions: list[str]

MCP protocol versions this server supports; the client should pick one for subsequent requests.

instructions class-attribute instance-attribute

instructions: str | None = None

Natural-language guidance describing the server and its features, e.g. for a system prompt. Should not duplicate information already in tool descriptions.

result_type class-attribute instance-attribute

result_type: ResultType = 'complete'

See ResultType. Always serialized; required on the 2026-07-28 wire, ignored by older peers, and defaulted on inbound bodies that omit it.

ElicitationCapability

Bases: MCPModel

Capability for elicitation operations.

Clients must support at least one mode (form or url).

Source code in src/mcp-types/mcp_types/_types.py

class ElicitationCapability(MCPModel):
    """Capability for elicitation operations.

    Clients must support at least one mode (form or url).
    """

    form: FormElicitationCapability | None = None
    """Present if the client supports form mode elicitation."""

    url: UrlElicitationCapability | None = None
    """Present if the client supports URL mode elicitation (2025-11-25 and later)."""

form class-attribute instance-attribute

form: FormElicitationCapability | None = None

Present if the client supports form mode elicitation.

url class-attribute instance-attribute

url: UrlElicitationCapability | None = None

Present if the client supports URL mode elicitation (2025-11-25 and later).

ElicitationRequiredErrorData

Bases: MCPModel

Error data for the -32042 URL-elicitation-required error.

Servers return this when a request cannot be processed until one or more URL mode elicitations are completed.

Removed in protocol 2026-07-28; sent/received on sessions negotiating 2025-11-25.

Source code in src/mcp-types/mcp_types/_types.py

class ElicitationRequiredErrorData(MCPModel):
    """Error data for the -32042 URL-elicitation-required error.

    Servers return this when a request cannot be processed until one or more
    URL mode elicitations are completed.

    Removed in protocol 2026-07-28; sent/received on sessions negotiating 2025-11-25.
    """

    elicitations: list[ElicitRequestURLParams]
    """List of URL mode elicitations that must be completed."""

elicitations instance-attribute

elicitations: list[ElicitRequestURLParams]

List of URL mode elicitations that must be completed.

ElicitCompleteNotification

Bases: Notification[ElicitCompleteNotificationParams, Literal['notifications/elicitation/complete']]

A notification from the server to the client, informing it that a URL mode elicitation has been completed.

Clients MAY use the notification to automatically retry requests that received a URLElicitationRequiredError, update the user interface, or otherwise continue an interaction. However, because delivery of the notification is not guaranteed, clients must not wait indefinitely for a notification from the server.

New in protocol 2025-11-25 with URL mode itself.

Source code in src/mcp-types/mcp_types/_types.py

class ElicitCompleteNotification(
    Notification[ElicitCompleteNotificationParams, Literal["notifications/elicitation/complete"]]
):
    """A notification from the server to the client, informing it that a URL mode
    elicitation has been completed.

    Clients MAY use the notification to automatically retry requests that received a
    URLElicitationRequiredError, update the user interface, or otherwise continue
    an interaction. However, because delivery of the notification is not guaranteed,
    clients must not wait indefinitely for a notification from the server.

    New in protocol 2025-11-25 with URL mode itself.
    """

    method: Literal["notifications/elicitation/complete"] = "notifications/elicitation/complete"
    params: ElicitCompleteNotificationParams

ElicitCompleteNotificationParams

Bases: NotificationParams

Parameters for elicitation completion notifications.

Source code in src/mcp-types/mcp_types/_types.py

class ElicitCompleteNotificationParams(NotificationParams):
    """Parameters for elicitation completion notifications."""

    elicitation_id: str
    """The unique identifier of the elicitation that was completed."""

elicitation_id instance-attribute

elicitation_id: str

The unique identifier of the elicitation that was completed.

ElicitRequest

Bases: Request[ElicitRequestParams, Literal['elicitation/create']]

A request from the server to elicit additional information from the user via the client.

Source code in src/mcp-types/mcp_types/_types.py

class ElicitRequest(Request[ElicitRequestParams, Literal["elicitation/create"]]):
    """A request from the server to elicit additional information from the user via the client."""

    method: Literal["elicitation/create"] = "elicitation/create"
    params: ElicitRequestParams

ElicitRequestFormParams

Bases: RequestParams

Parameters for form mode elicitation requests.

Form mode collects non-sensitive information from the user via an in-band form rendered by the client.

Source code in src/mcp-types/mcp_types/_types.py

class ElicitRequestFormParams(RequestParams):
    """Parameters for form mode elicitation requests.

    Form mode collects non-sensitive information from the user via an in-band form
    rendered by the client.
    """

    mode: Literal["form"] = "form"
    """The elicitation mode (always "form" for this type)."""

    message: str
    """The message to present to the user describing what information is being requested."""

    requested_schema: ElicitRequestedSchema
    """
    A restricted subset of JSON Schema defining the structure of the expected response.
    Only top-level properties are allowed, without nesting.
    """

    task: TaskMetadata | None = None
    """If specified, the caller requests task-augmented execution (2025-11-25 only)."""

mode class-attribute instance-attribute

mode: Literal['form'] = 'form'

The elicitation mode (always "form" for this type).

message instance-attribute

message: str

The message to present to the user describing what information is being requested.

requested_schema instance-attribute

requested_schema: ElicitRequestedSchema

A restricted subset of JSON Schema defining the structure of the expected response. Only top-level properties are allowed, without nesting.

task class-attribute instance-attribute

task: TaskMetadata | None = None

If specified, the caller requests task-augmented execution (2025-11-25 only).

ElicitRequestParams module-attribute

ElicitRequestParams: TypeAlias = (
    ElicitRequestURLParams | ElicitRequestFormParams
)

Parameters for elicitation requests - either form or URL mode.

ElicitRequestURLParams

Bases: RequestParams

Parameters for URL mode elicitation requests.

URL mode directs users to external URLs for sensitive out-of-band interactions like OAuth flows, credential collection, or payment processing. New in 2025-11-25.

Source code in src/mcp-types/mcp_types/_types.py

class ElicitRequestURLParams(RequestParams):
    """Parameters for URL mode elicitation requests.

    URL mode directs users to external URLs for sensitive out-of-band interactions
    like OAuth flows, credential collection, or payment processing. New in 2025-11-25.
    """

    mode: Literal["url"] = "url"
    """The elicitation mode (always "url" for this type)."""

    message: str
    """The message to present to the user explaining why the interaction is needed."""

    url: str
    """The URL that the user should navigate to."""

    elicitation_id: str | None = None
    """The ID of the elicitation, which must be unique within the context of the server.

    The client MUST treat this ID as an opaque value. Required on the wire at
    2025-11-25; removed at 2026-07-28.
    """

    task: TaskMetadata | None = None
    """If specified, the caller requests task-augmented execution (2025-11-25 only)."""

mode class-attribute instance-attribute

mode: Literal['url'] = 'url'

The elicitation mode (always "url" for this type).

message instance-attribute

message: str

The message to present to the user explaining why the interaction is needed.

url instance-attribute

url: str

The URL that the user should navigate to.

elicitation_id class-attribute instance-attribute

elicitation_id: str | None = None

The ID of the elicitation, which must be unique within the context of the server.

The client MUST treat this ID as an opaque value. Required on the wire at 2025-11-25; removed at 2026-07-28.

task class-attribute instance-attribute

task: TaskMetadata | None = None

If specified, the caller requests task-augmented execution (2025-11-25 only).

ElicitResult

Bases: Result

The client's response to an elicitation request.

Source code in src/mcp-types/mcp_types/_types.py

class ElicitResult(Result):
    """The client's response to an elicitation request."""

    action: Literal["accept", "decline", "cancel"]
    """
    The user action in response to the elicitation.
    - "accept": User submitted the form/confirmed the action (or consented to URL navigation)
    - "decline": User explicitly declined the action
    - "cancel": User dismissed without making an explicit choice
    """

    content: dict[str, str | int | float | bool | list[str] | None] | None = None
    """
    The submitted form data, only present when action is "accept" in form mode.
    Contains values matching the requested schema. Values can be strings, integers, floats,
    booleans, arrays of strings, or null.
    For URL mode, this field is omitted.
    """

action instance-attribute

action: Literal['accept', 'decline', 'cancel']

The user action in response to the elicitation. - "accept": User submitted the form/confirmed the action (or consented to URL navigation) - "decline": User explicitly declined the action - "cancel": User dismissed without making an explicit choice

content class-attribute instance-attribute

content: (
    dict[str, str | int | float | bool | list[str] | None]
    | None
) = None

The submitted form data, only present when action is "accept" in form mode. Contains values matching the requested schema. Values can be strings, integers, floats, booleans, arrays of strings, or null. For URL mode, this field is omitted.

EmbeddedResource

Bases: MCPModel

The contents of a resource, embedded into a prompt or tool call result.

It is up to the client how best to render embedded resources for the benefit of the LLM and/or the user.

Source code in src/mcp-types/mcp_types/_types.py

class EmbeddedResource(MCPModel):
    """The contents of a resource, embedded into a prompt or tool call result.

    It is up to the client how best to render embedded resources for the benefit
    of the LLM and/or the user.
    """

    type: Literal["resource"] = "resource"
    resource: TextResourceContents | BlobResourceContents
    annotations: Annotations | None = None
    """Optional annotations for the client."""
    meta: Meta | None = Field(alias="_meta", default=None)
    """
    See [MCP specification](https://github.com/modelcontextprotocol/modelcontextprotocol/blob/47339c03c143bb4ec01a26e721a1b8fe66634ebe/docs/specification/draft/basic/index.mdx#general-fields)
    for notes on _meta usage.
    """

annotations class-attribute instance-attribute

annotations: Annotations | None = None

Optional annotations for the client.

meta class-attribute instance-attribute

meta: Meta | None = Field(alias='_meta', default=None)

See MCP specification for notes on _meta usage.

EmptyResult

Bases: Result

A result that indicates success but carries no data.

result_type defaults to None so this dumps as {}: deployed TypeScript and Rust SDK peers (clients and servers) validate empty results strictly and reject extra keys. The 2026-07-28 schema requires resultType, so code answering an empty result on a 2026-07-28+ session must pass result_type="complete".

Source code in src/mcp-types/mcp_types/_types.py

class EmptyResult(Result):
    """A result that indicates success but carries no data.

    `result_type` defaults to None so this dumps as `{}`: deployed TypeScript
    and Rust SDK peers (clients and servers) validate empty results strictly
    and reject extra keys. The 2026-07-28 schema requires `resultType`, so code
    answering an empty result on a 2026-07-28+ session must pass
    `result_type="complete"`.
    """

    result_type: ResultType | None = None
    """None keeps the dump empty; see the class docstring."""

result_type class-attribute instance-attribute

result_type: ResultType | None = None

None keeps the dump empty; see the class docstring.

FormElicitationCapability

Bases: MCPModel

Capability for form mode elicitation.

Source code in src/mcp-types/mcp_types/_types.py

class FormElicitationCapability(MCPModel):
    """Capability for form mode elicitation."""

GetPromptRequest

Bases: Request[GetPromptRequestParams, Literal['prompts/get']]

Used by the client to get a prompt provided by the server.

Source code in src/mcp-types/mcp_types/_types.py

class GetPromptRequest(Request[GetPromptRequestParams, Literal["prompts/get"]]):
    """Used by the client to get a prompt provided by the server."""

    method: Literal["prompts/get"] = "prompts/get"
    params: GetPromptRequestParams

GetPromptRequestParams

Bases: InputResponseRequestParams

Source code in src/mcp-types/mcp_types/_types.py

class GetPromptRequestParams(InputResponseRequestParams):
    name: str
    """The name of the prompt or prompt template."""
    arguments: dict[str, str] | None = None
    """Arguments to use for templating the prompt."""

name instance-attribute

name: str

The name of the prompt or prompt template.

arguments class-attribute instance-attribute

arguments: dict[str, str] | None = None

Arguments to use for templating the prompt.

GetPromptResult

Bases: Result

The server's response to a prompts/get request from the client.

Source code in src/mcp-types/mcp_types/_types.py

class GetPromptResult(Result):
    """The server's response to a prompts/get request from the client."""

    description: str | None = None
    """An optional description for the prompt."""
    messages: list[PromptMessage]
    """The messages composing the prompt, in the order they should be presented."""

    result_type: ResultType = "complete"
    """See `ResultType`. Always serialized; older peers ignore it."""

description class-attribute instance-attribute

description: str | None = None

An optional description for the prompt.

messages instance-attribute

messages: list[PromptMessage]

The messages composing the prompt, in the order they should be presented.

result_type class-attribute instance-attribute

result_type: ResultType = 'complete'

See ResultType. Always serialized; older peers ignore it.

GetTaskPayloadRequest

Bases: Request[GetTaskPayloadRequestParams, Literal['tasks/result']]

A request to retrieve the result of a completed task (2025-11-25 only).

Source code in src/mcp-types/mcp_types/_types.py

class GetTaskPayloadRequest(Request[GetTaskPayloadRequestParams, Literal["tasks/result"]]):
    """A request to retrieve the result of a completed task (2025-11-25 only)."""

    method: Literal["tasks/result"] = "tasks/result"
    params: GetTaskPayloadRequestParams

GetTaskPayloadRequestParams

Bases: RequestParams

Parameters for a tasks/result request.

Source code in src/mcp-types/mcp_types/_types.py

class GetTaskPayloadRequestParams(RequestParams):
    """Parameters for a tasks/result request."""

    task_id: str

GetTaskPayloadResult

Bases: Result

The response to a tasks/result request (2025-11-25 only).

The structure matches the result type of the original request. The payload arrives as extra wire fields, which MCPModel does not retain; validate the response into the original request's result type (e.g. CallToolResult) instead of this class.

Source code in src/mcp-types/mcp_types/_types.py

class GetTaskPayloadResult(Result):
    """The response to a tasks/result request (2025-11-25 only).

    The structure matches the result type of the original request. The payload
    arrives as extra wire fields, which `MCPModel` does not retain; validate the
    response into the original request's result type (e.g. `CallToolResult`)
    instead of this class.
    """

GetTaskRequest

Bases: Request[GetTaskRequestParams, Literal['tasks/get']]

A request to retrieve the state of a task (2025-11-25 only).

Source code in src/mcp-types/mcp_types/_types.py

class GetTaskRequest(Request[GetTaskRequestParams, Literal["tasks/get"]]):
    """A request to retrieve the state of a task (2025-11-25 only)."""

    method: Literal["tasks/get"] = "tasks/get"
    params: GetTaskRequestParams

GetTaskResult

Bases: Result, Task

The response to a tasks/get request (2025-11-25 only).

Source code in src/mcp-types/mcp_types/_types.py

class GetTaskResult(Result, Task):
    """The response to a tasks/get request (2025-11-25 only)."""

Icon

Bases: MCPModel

An optionally-sized icon for display in a user interface (2025-11-25+).

Source code in src/mcp-types/mcp_types/_types.py

class Icon(MCPModel):
    """An optionally-sized icon for display in a user interface (2025-11-25+)."""

    src: str
    """A standard URI pointing to an icon resource (`http(s):` or `data:`).

    Consumers SHOULD ensure icon URLs come from a trusted domain and SHOULD
    take appropriate precautions when consuming SVGs (which can contain script).
    """

    mime_type: str | None = None
    """Optional MIME type override if the source MIME type is missing or generic."""

    sizes: list[str] | None = None
    """Optional sizes this icon is available in: WxH (e.g. `"48x48"`) or `"any"`.
    If not provided, assume the icon can be used at any size."""

    theme: IconTheme | None = None
    """The theme this icon is designed for. If not provided, assume any theme."""

src instance-attribute

src: str

A standard URI pointing to an icon resource (http(s): or data:).

Consumers SHOULD ensure icon URLs come from a trusted domain and SHOULD take appropriate precautions when consuming SVGs (which can contain script).

mime_type class-attribute instance-attribute

mime_type: str | None = None

Optional MIME type override if the source MIME type is missing or generic.

sizes class-attribute instance-attribute

sizes: list[str] | None = None

Optional sizes this icon is available in: WxH (e.g. "48x48") or "any". If not provided, assume the icon can be used at any size.

theme class-attribute instance-attribute

theme: IconTheme | None = None

The theme this icon is designed for. If not provided, assume any theme.

IconTheme module-attribute

IconTheme = Literal['light', 'dark']

Theme an icon is designed for. Wire values of Icon.theme (2025-11-25+).

ImageContent

Bases: MCPModel

An image provided to or from an LLM.

Source code in src/mcp-types/mcp_types/_types.py

class ImageContent(MCPModel):
    """An image provided to or from an LLM."""

    type: Literal["image"] = "image"
    data: str
    """The base64-encoded image data."""
    mime_type: str
    """
    The MIME type of the image. Different providers may support different
    image types.
    """
    annotations: Annotations | None = None
    """Optional annotations for the client."""
    meta: Meta | None = Field(alias="_meta", default=None)
    """See the MCP specification's "General fields: _meta" section for notes on _meta usage."""

data instance-attribute

data: str

The base64-encoded image data.

mime_type instance-attribute

mime_type: str

The MIME type of the image. Different providers may support different image types.

annotations class-attribute instance-attribute

annotations: Annotations | None = None

Optional annotations for the client.

meta class-attribute instance-attribute

meta: Meta | None = Field(alias='_meta', default=None)

See the MCP specification's "General fields: _meta" section for notes on _meta usage.

Implementation

Bases: BaseMetadata

Describes the name and version of an MCP implementation (clientInfo / serverInfo).

Source code in src/mcp-types/mcp_types/_types.py

class Implementation(BaseMetadata):
    """Describes the name and version of an MCP implementation (`clientInfo` / `serverInfo`)."""

    version: str
    description: str | None = None
    """An optional human-readable description of what this implementation does."""

    website_url: str | None = None
    """An optional URL of the website for this implementation."""

    icons: list[Icon] | None = None
    """Optional set of sized icons that the client can display in a user interface."""

description class-attribute instance-attribute

description: str | None = None

An optional human-readable description of what this implementation does.

website_url class-attribute instance-attribute

website_url: str | None = None

An optional URL of the website for this implementation.

icons class-attribute instance-attribute

icons: list[Icon] | None = None

Optional set of sized icons that the client can display in a user interface.

IncludeContext module-attribute

IncludeContext = Literal["none", "thisServer", "allServers"]

Scope of MCP-server context a sampling request asks the client to attach.

"thisServer" and "allServers" are deprecated (SEP-2596).

InitializedNotification

Bases: Notification[NotificationParams | None, Literal['notifications/initialized']]

This notification is sent from the client to the server after initialization has finished.

Removed in protocol 2026-07-28; sent/received on sessions negotiating <= 2025-11-25.

Source code in src/mcp-types/mcp_types/_types.py

class InitializedNotification(Notification[NotificationParams | None, Literal["notifications/initialized"]]):
    """This notification is sent from the client to the server after initialization has
    finished.

    Removed in protocol 2026-07-28; sent/received on sessions negotiating <= 2025-11-25.
    """

    method: Literal["notifications/initialized"] = "notifications/initialized"
    params: NotificationParams | None = None

InitializeRequest

Bases: Request[InitializeRequestParams, Literal['initialize']]

This request is sent from the client to the server when it first connects, asking it to begin initialization.

Removed in protocol 2026-07-28; sent/received on sessions negotiating <= 2025-11-25. On 2026-07-28 the handshake is server/discover plus per-request _meta.

Source code in src/mcp-types/mcp_types/_types.py

class InitializeRequest(Request[InitializeRequestParams, Literal["initialize"]]):
    """This request is sent from the client to the server when it first connects, asking it
    to begin initialization.

    Removed in protocol 2026-07-28; sent/received on sessions negotiating <= 2025-11-25.
    On 2026-07-28 the handshake is `server/discover` plus per-request `_meta`.
    """

    method: Literal["initialize"] = "initialize"
    params: InitializeRequestParams

InitializeRequestParams

Bases: RequestParams

Parameters for the initialize request.

Removed in protocol 2026-07-28; sent/received on sessions negotiating <= 2025-11-25.

Source code in src/mcp-types/mcp_types/_types.py

class InitializeRequestParams(RequestParams):
    """Parameters for the `initialize` request.

    Removed in protocol 2026-07-28; sent/received on sessions negotiating <= 2025-11-25.
    """

    protocol_version: str
    """The latest version of the Model Context Protocol that the client supports."""
    capabilities: ClientCapabilities
    client_info: Implementation

protocol_version instance-attribute

protocol_version: str

The latest version of the Model Context Protocol that the client supports.

InitializeResult

Bases: Result

After receiving an initialize request from the client, the server sends this response.

Removed in protocol 2026-07-28; sent/received on sessions negotiating <= 2025-11-25.

Source code in src/mcp-types/mcp_types/_types.py

class InitializeResult(Result):
    """After receiving an initialize request from the client, the server sends this response.

    Removed in protocol 2026-07-28; sent/received on sessions negotiating <= 2025-11-25.
    """

    protocol_version: str
    """The version of the Model Context Protocol that the server wants to use.
    If the client cannot support this version, it MUST disconnect."""
    capabilities: ServerCapabilities
    server_info: Implementation
    instructions: str | None = None
    """Instructions describing how to use the server and its features.

    Clients may use this to improve an LLM's understanding of available tools,
    resources, etc., for example by adding it to the system prompt.
    """

protocol_version instance-attribute

protocol_version: str

The version of the Model Context Protocol that the server wants to use. If the client cannot support this version, it MUST disconnect.

instructions class-attribute instance-attribute

instructions: str | None = None

Instructions describing how to use the server and its features.

Clients may use this to improve an LLM's understanding of available tools, resources, etc., for example by adding it to the system prompt.

InputRequest module-attribute

InputRequest: TypeAlias = (
    CreateMessageRequest | ListRootsRequest | ElicitRequest
)

A single server-initiated input request embedded in InputRequiredResult (2026-07-28).

Discriminated by method. On 2026-07-28 these embedded payloads take the place of standalone server-to-client JSON-RPC requests.

InputRequests module-attribute

InputRequests: TypeAlias = dict[str, InputRequest]

A map of server-initiated requests that the client must fulfill (2026-07-28).

Keys are server-assigned identifiers. Carried by InputRequiredResult.input_requests and by the tasks extension.

InputRequiredResult

Bases: Result

The server needs additional input before the original request can complete (2026-07-28).

Returned in place of the normal result of an interactive client request (tools/call, prompts/get, resources/read). The client fulfills input_requests and retries the original request, carrying the responses and the echoed request_state. At least one of those two fields is present on the wire (spec MUST).

Source code in src/mcp-types/mcp_types/_types.py

class InputRequiredResult(Result):
    """The server needs additional input before the original request can complete (2026-07-28).

    Returned in place of the normal result of an interactive client request
    (`tools/call`, `prompts/get`, `resources/read`). The client fulfills
    `input_requests` and retries the original request, carrying the responses
    and the echoed `request_state`. At least one of those two fields is
    present on the wire (spec MUST).
    """

    result_type: Literal["input_required"] = "input_required"
    """Discriminating tag for the dual-result response unions."""

    input_requests: InputRequests | None = None
    """Requests the client must complete before retrying. Keys are server-assigned."""

    request_state: str | None = None
    """Opaque state to pass back verbatim when the client retries the original request."""

    @model_validator(mode="after")
    def _require_one_field(self) -> Self:
        if not self.input_requests and self.request_state is None:
            raise ValueError("InputRequiredResult requires at least one of input_requests or request_state")
        return self

result_type class-attribute instance-attribute

result_type: Literal['input_required'] = 'input_required'

Discriminating tag for the dual-result response unions.

input_requests class-attribute instance-attribute

input_requests: InputRequests | None = None

Requests the client must complete before retrying. Keys are server-assigned.

request_state class-attribute instance-attribute

request_state: str | None = None

Opaque state to pass back verbatim when the client retries the original request.

InputResponse module-attribute

InputResponse: TypeAlias = (
    CreateMessageResult
    | CreateMessageResultWithTools
    | ListRootsResult
    | ElicitResult
)

A client response to a single server-initiated input request (2026-07-28).

CreateMessageResultWithTools is this SDK's array-content split of the schema's single CreateMessageResult arm; the wire union has three arms.

InputResponseRequestParams

Bases: RequestParams

Base params for client requests that can carry responses to a server's input requests (2026-07-28 multi-round-trip flow).

When a request returns an InputRequiredResult, the client retries the original request with these fields populated.

Source code in src/mcp-types/mcp_types/_types.py

class InputResponseRequestParams(RequestParams):
    """Base params for client requests that can carry responses to a server's
    input requests (2026-07-28 multi-round-trip flow).

    When a request returns an `InputRequiredResult`, the client retries the
    original request with these fields populated.
    """

    input_responses: InputResponses | None = None
    """Responses to the server's `InputRequiredResult.input_requests`, keyed identically."""
    request_state: str | None = None
    """Opaque state from the `InputRequiredResult`, passed back verbatim on retry."""

input_responses class-attribute instance-attribute

input_responses: InputResponses | None = None

Responses to the server's InputRequiredResult.input_requests, keyed identically.

request_state class-attribute instance-attribute

request_state: str | None = None

Opaque state from the InputRequiredResult, passed back verbatim on retry.

InputResponses module-attribute

InputResponses: TypeAlias = dict[str, InputResponse]

A map of client responses to server-initiated input requests (2026-07-28).

Keys match those of the InputRequests map the server sent. Also used by the tasks extension's tasks/update params.

ListPromptsRequest

Bases: PaginatedRequest[Literal['prompts/list']]

Sent from the client to request a list of prompts and prompt templates the server has.

Source code in src/mcp-types/mcp_types/_types.py

class ListPromptsRequest(PaginatedRequest[Literal["prompts/list"]]):
    """Sent from the client to request a list of prompts and prompt templates the server has."""

    method: Literal["prompts/list"] = "prompts/list"

ListPromptsResult

Bases: PaginatedResult, CacheableResult

The server's response to a prompts/list request from the client.

Source code in src/mcp-types/mcp_types/_types.py

class ListPromptsResult(PaginatedResult, CacheableResult):
    """The server's response to a prompts/list request from the client."""

    prompts: list[Prompt]
    result_type: ResultType = "complete"
    """See `ResultType`. Always serialized; older peers ignore it."""

result_type class-attribute instance-attribute

result_type: ResultType = 'complete'

See ResultType. Always serialized; older peers ignore it.

ListResourcesRequest

Bases: PaginatedRequest[Literal['resources/list']]

Sent from the client to request a list of resources the server has.

Source code in src/mcp-types/mcp_types/_types.py

class ListResourcesRequest(PaginatedRequest[Literal["resources/list"]]):
    """Sent from the client to request a list of resources the server has."""

    method: Literal["resources/list"] = "resources/list"

ListResourcesResult

Bases: PaginatedResult, CacheableResult

The server's response to a resources/list request from the client.

Source code in src/mcp-types/mcp_types/_types.py

class ListResourcesResult(PaginatedResult, CacheableResult):
    """The server's response to a resources/list request from the client."""

    resources: list[Resource]
    result_type: ResultType = "complete"
    """See `ResultType`. Always serialized; older peers ignore it."""

result_type class-attribute instance-attribute

result_type: ResultType = 'complete'

See ResultType. Always serialized; older peers ignore it.

ListResourceTemplatesRequest

Bases: PaginatedRequest[Literal['resources/templates/list']]

Sent from the client to request a list of resource templates the server has.

Source code in src/mcp-types/mcp_types/_types.py

class ListResourceTemplatesRequest(PaginatedRequest[Literal["resources/templates/list"]]):
    """Sent from the client to request a list of resource templates the server has."""

    method: Literal["resources/templates/list"] = "resources/templates/list"

ListResourceTemplatesResult

Bases: PaginatedResult, CacheableResult

The server's response to a resources/templates/list request from the client.

Source code in src/mcp-types/mcp_types/_types.py

class ListResourceTemplatesResult(PaginatedResult, CacheableResult):
    """The server's response to a resources/templates/list request from the client."""

    resource_templates: list[ResourceTemplate]
    result_type: ResultType = "complete"
    """See `ResultType`. Always serialized; older peers ignore it."""

result_type class-attribute instance-attribute

result_type: ResultType = 'complete'

See ResultType. Always serialized; older peers ignore it.

ListRootsRequest

Bases: Request[RequestParams | None, Literal['roots/list']]

Sent from the server to request a list of root URIs from the client. Roots allow servers to ask for specific directories or files to operate on. A common example for roots is providing a set of repositories or directories a server should operate on.

This request is typically used when the server needs to understand the file system structure or access specific locations that the client has permission to read from.

A standalone JSON-RPC request through 2025-11-25; on 2026-07-28 it is embedded in InputRequiredResult.input_requests. Deprecated in 2026-07-28 (SEP-2577).

Source code in src/mcp-types/mcp_types/_types.py

class ListRootsRequest(Request[RequestParams | None, Literal["roots/list"]]):
    """Sent from the server to request a list of root URIs from the client. Roots allow
    servers to ask for specific directories or files to operate on. A common example
    for roots is providing a set of repositories or directories a server should operate
    on.

    This request is typically used when the server needs to understand the file system
    structure or access specific locations that the client has permission to read from.

    A standalone JSON-RPC request through 2025-11-25; on 2026-07-28 it is
    embedded in `InputRequiredResult.input_requests`. Deprecated in 2026-07-28 (SEP-2577).
    """

    method: Literal["roots/list"] = "roots/list"
    params: RequestParams | None = None
    """Stays optional on 2026-07-28 (reserved client `_meta` keys do not apply
    to server-to-client payloads)."""

params class-attribute instance-attribute

params: RequestParams | None = None

Stays optional on 2026-07-28 (reserved client _meta keys do not apply to server-to-client payloads).

ListRootsResult

Bases: Result

The client's response to a roots/list request from the server.

This result contains an array of Root objects, each representing a root directory or file that the server can operate on.

On 2026-07-28 this is carried as an InputResponses entry, not a JSON-RPC result. Deprecated in 2026-07-28 (SEP-2577).

Source code in src/mcp-types/mcp_types/_types.py

class ListRootsResult(Result):
    """The client's response to a roots/list request from the server.

    This result contains an array of Root objects, each representing a root
    directory or file that the server can operate on.

    On 2026-07-28 this is carried as an `InputResponses` entry, not a JSON-RPC
    result. Deprecated in 2026-07-28 (SEP-2577).
    """

    roots: list[Root]

ListTasksRequest

Bases: PaginatedRequest[Literal['tasks/list']]

A request to retrieve a list of tasks (2025-11-25 only).

Source code in src/mcp-types/mcp_types/_types.py

class ListTasksRequest(PaginatedRequest[Literal["tasks/list"]]):
    """A request to retrieve a list of tasks (2025-11-25 only)."""

    method: Literal["tasks/list"] = "tasks/list"

ListTasksResult

Bases: PaginatedResult

The response to a tasks/list request (2025-11-25 only).

Source code in src/mcp-types/mcp_types/_types.py

class ListTasksResult(PaginatedResult):
    """The response to a tasks/list request (2025-11-25 only)."""

    tasks: list[Task]

ListToolsRequest

Bases: PaginatedRequest[Literal['tools/list']]

Sent from the client to request a list of tools the server has.

Source code in src/mcp-types/mcp_types/_types.py

class ListToolsRequest(PaginatedRequest[Literal["tools/list"]]):
    """Sent from the client to request a list of tools the server has."""

    method: Literal["tools/list"] = "tools/list"

ListToolsResult

Bases: PaginatedResult, CacheableResult

The server's response to a tools/list request from the client.

Source code in src/mcp-types/mcp_types/_types.py

class ListToolsResult(PaginatedResult, CacheableResult):
    """The server's response to a tools/list request from the client."""

    tools: list[Tool]

    result_type: ResultType = "complete"
    """See `ResultType`. Always serialized; older peers ignore it."""

result_type class-attribute instance-attribute

result_type: ResultType = 'complete'

See ResultType. Always serialized; older peers ignore it.

LoggingCapability

Bases: MCPModel

Capability for logging operations.

Source code in src/mcp-types/mcp_types/_types.py

class LoggingCapability(MCPModel):
    """Capability for logging operations."""

LoggingLevel module-attribute

LoggingLevel = Literal[
    "debug",
    "info",
    "notice",
    "warning",
    "error",
    "critical",
    "alert",
    "emergency",
]

The severity of a log message.

These map to syslog severities (RFC-5424 section 6.2.1). Logging is deprecated in 2026-07-28 (SEP-2577); the level scale is unchanged across versions.

LoggingMessageNotification

Bases: Notification[LoggingMessageNotificationParams, Literal['notifications/message']]

Notification of a log message passed from server to client.

Through 2025-11-25 the client subscribes via logging/setLevel. On 2026-07-28 the client opts in per-request via _meta (LOG_LEVEL_META_KEY) and the server MUST NOT send this without it. Deprecated in 2026-07-28 (SEP-2577).

Source code in src/mcp-types/mcp_types/_types.py

class LoggingMessageNotification(Notification[LoggingMessageNotificationParams, Literal["notifications/message"]]):
    """Notification of a log message passed from server to client.

    Through 2025-11-25 the client subscribes via `logging/setLevel`. On
    2026-07-28 the client opts in per-request via `_meta` (`LOG_LEVEL_META_KEY`)
    and the server MUST NOT send this without it. Deprecated in 2026-07-28 (SEP-2577).
    """

    method: Literal["notifications/message"] = "notifications/message"
    params: LoggingMessageNotificationParams

LoggingMessageNotificationParams

Bases: NotificationParams

Source code in src/mcp-types/mcp_types/_types.py

class LoggingMessageNotificationParams(NotificationParams):
    level: LoggingLevel
    """The severity of this log message."""
    logger: str | None = None
    """An optional name of the logger issuing this message."""
    data: Any
    """
    The data to be logged, such as a string message or an object. Any JSON serializable
    type is allowed here.
    """

level instance-attribute

level: LoggingLevel

The severity of this log message.

logger class-attribute instance-attribute

logger: str | None = None

An optional name of the logger issuing this message.

data instance-attribute

data: Any

The data to be logged, such as a string message or an object. Any JSON serializable type is allowed here.

MissingRequiredClientCapabilityErrorData

Bases: MCPModel

Error data for the -32021 missing-required-client-capability error (2026-07-28).

Source code in src/mcp-types/mcp_types/_types.py

class MissingRequiredClientCapabilityErrorData(MCPModel):
    """Error data for the -32021 missing-required-client-capability error (2026-07-28)."""

    required_capabilities: ClientCapabilities
    """The capabilities the server requires from the client to process this request."""

required_capabilities instance-attribute

required_capabilities: ClientCapabilities

The capabilities the server requires from the client to process this request.

ModelHint

Bases: MCPModel

Hints to use for model selection.

Keys not declared here are up to the client to interpret. Deprecated in 2026-07-28 (SEP-2577) with the rest of sampling.

Source code in src/mcp-types/mcp_types/_types.py

class ModelHint(MCPModel):
    """Hints to use for model selection.

    Keys not declared here are up to the client to interpret. Deprecated in
    2026-07-28 (SEP-2577) with the rest of sampling.
    """

    name: str | None = None
    """A hint for a model name.

    The client SHOULD treat this as a substring (e.g. `sonnet` matches
    `claude-3-5-sonnet-20241022`) and MAY map it to another provider's model
    that fills a similar niche.
    """

name class-attribute instance-attribute

name: str | None = None

A hint for a model name.

The client SHOULD treat this as a substring (e.g. sonnet matches claude-3-5-sonnet-20241022) and MAY map it to another provider's model that fills a similar niche.

ModelPreferences

Bases: MCPModel

The server's preferences for model selection, requested of the client during sampling.

Because LLMs can vary along multiple dimensions, choosing the "best" model is rarely straightforward. Different models excel in different areas—some are faster but less capable, others are more capable but more expensive, and so on. This interface allows servers to express their priorities across multiple dimensions to help clients make an appropriate selection for their use case.

These preferences are always advisory. The client MAY ignore them. It is also up to the client to decide how to interpret these preferences and how to balance them against other considerations.

Deprecated in 2026-07-28 (SEP-2577) with the rest of sampling.

Source code in src/mcp-types/mcp_types/_types.py

class ModelPreferences(MCPModel):
    """The server's preferences for model selection, requested of the client during
    sampling.

    Because LLMs can vary along multiple dimensions, choosing the "best" model is
    rarely straightforward. Different models excel in different areas—some are
    faster but less capable, others are more capable but more expensive, and so
    on. This interface allows servers to express their priorities across multiple
    dimensions to help clients make an appropriate selection for their use case.

    These preferences are always advisory. The client MAY ignore them. It is also
    up to the client to decide how to interpret these preferences and how to
    balance them against other considerations.

    Deprecated in 2026-07-28 (SEP-2577) with the rest of sampling.
    """

    hints: list[ModelHint] | None = None
    """
    Optional hints to use for model selection.

    If multiple hints are specified, the client MUST evaluate them in order
    (such that the first match is taken).

    The client SHOULD prioritize these hints over the numeric priorities, but
    MAY still use the priorities to select from ambiguous matches.
    """

    cost_priority: float | None = None
    """
    How much to prioritize cost when selecting a model. A value of 0 means cost
    is not important, while a value of 1 means cost is the most important
    factor.
    """

    speed_priority: float | None = None
    """
    How much to prioritize sampling speed (latency) when selecting a model. A
    value of 0 means speed is not important, while a value of 1 means speed is
    the most important factor.
    """

    intelligence_priority: float | None = None
    """
    How much to prioritize intelligence and capabilities when selecting a
    model. A value of 0 means intelligence is not important, while a value of 1
    means intelligence is the most important factor.
    """

hints class-attribute instance-attribute

hints: list[ModelHint] | None = None

Optional hints to use for model selection.

If multiple hints are specified, the client MUST evaluate them in order (such that the first match is taken).

The client SHOULD prioritize these hints over the numeric priorities, but MAY still use the priorities to select from ambiguous matches.

cost_priority class-attribute instance-attribute

cost_priority: float | None = None

How much to prioritize cost when selecting a model. A value of 0 means cost is not important, while a value of 1 means cost is the most important factor.

speed_priority class-attribute instance-attribute

speed_priority: float | None = None

How much to prioritize sampling speed (latency) when selecting a model. A value of 0 means speed is not important, while a value of 1 means speed is the most important factor.

intelligence_priority class-attribute instance-attribute

intelligence_priority: float | None = None

How much to prioritize intelligence and capabilities when selecting a model. A value of 0 means intelligence is not important, while a value of 1 means intelligence is the most important factor.

Notification

Bases: MCPModel, Generic[NotificationParamsT, MethodT]

Base class for JSON-RPC notifications.

Source code in src/mcp-types/mcp_types/_types.py

class Notification(MCPModel, Generic[NotificationParamsT, MethodT]):
    """Base class for JSON-RPC notifications."""

    method: MethodT
    params: NotificationParamsT

NotificationParams

Bases: MCPModel

Source code in src/mcp-types/mcp_types/_types.py

class NotificationParams(MCPModel):
    meta: Meta | None = Field(alias="_meta", default=None)
    """
    See [MCP specification](https://github.com/modelcontextprotocol/modelcontextprotocol/blob/47339c03c143bb4ec01a26e721a1b8fe66634ebe/docs/specification/draft/basic/index.mdx#general-fields)
    for notes on _meta usage.
    """

meta class-attribute instance-attribute

meta: Meta | None = Field(alias='_meta', default=None)

See MCP specification for notes on _meta usage.

PaginatedRequest

Bases: Request[PaginatedRequestParams | None, MethodT], Generic[MethodT]

Base class for paginated requests, matching the schema's PaginatedRequest interface.

Source code in src/mcp-types/mcp_types/_types.py

class PaginatedRequest(Request[PaginatedRequestParams | None, MethodT], Generic[MethodT]):
    """Base class for paginated requests, matching the schema's PaginatedRequest interface."""

    params: PaginatedRequestParams | None = None
    """Pagination params. Required on the 2026-07-28+ wire (because `_meta` is);
    the session layer materializes it there. Optional on earlier versions."""

params class-attribute instance-attribute

params: PaginatedRequestParams | None = None

Pagination params. Required on the 2026-07-28+ wire (because _meta is); the session layer materializes it there. Optional on earlier versions.

PaginatedRequestParams

Bases: RequestParams

Source code in src/mcp-types/mcp_types/_types.py

class PaginatedRequestParams(RequestParams):
    cursor: str | None = None
    """An opaque token representing the current pagination position.

    If provided, the server should return results starting after this cursor.
    """

cursor class-attribute instance-attribute

cursor: str | None = None

An opaque token representing the current pagination position.

If provided, the server should return results starting after this cursor.

PaginatedResult

Bases: Result

Source code in src/mcp-types/mcp_types/_types.py

class PaginatedResult(Result):
    next_cursor: str | None = None
    """
    An opaque token representing the pagination position after the last returned result.
    If present, there may be more results available.
    """

next_cursor class-attribute instance-attribute

next_cursor: str | None = None

An opaque token representing the pagination position after the last returned result. If present, there may be more results available.

PingRequest

Bases: Request[RequestParams | None, Literal['ping']]

A ping, issued by either the server or the client, to check that the other party is still alive. The receiver must promptly respond, or else may be disconnected.

Removed in protocol 2026-07-28; sent/received on sessions negotiating <= 2025-11-25.

Source code in src/mcp-types/mcp_types/_types.py

class PingRequest(Request[RequestParams | None, Literal["ping"]]):
    """A ping, issued by either the server or the client, to check that the other party is
    still alive. The receiver must promptly respond, or else may be disconnected.

    Removed in protocol 2026-07-28; sent/received on sessions negotiating <= 2025-11-25.
    """

    method: Literal["ping"] = "ping"
    params: RequestParams | None = None

ProgressNotification

Bases: Notification[ProgressNotificationParams, Literal['notifications/progress']]

An out-of-band notification used to inform the receiver of a progress update for a long-running request.

Source code in src/mcp-types/mcp_types/_types.py

class ProgressNotification(Notification[ProgressNotificationParams, Literal["notifications/progress"]]):
    """An out-of-band notification used to inform the receiver of a progress update for a long-running request."""

    method: Literal["notifications/progress"] = "notifications/progress"
    params: ProgressNotificationParams

ProgressNotificationParams

Bases: NotificationParams

Parameters for progress notifications.

Source code in src/mcp-types/mcp_types/_types.py

class ProgressNotificationParams(NotificationParams):
    """Parameters for progress notifications."""

    progress_token: ProgressToken
    """
    The progress token which was given in the initial request, used to associate this
    notification with the request that is proceeding.
    """
    progress: float
    """
    The progress thus far. This should increase every time progress is made, even if the
    total is unknown.
    """
    total: float | None = None
    """Total number of items to process (or total progress required), if known."""
    message: str | None = None
    """Message related to progress.

    This should provide relevant human-readable progress information.
    """

progress_token instance-attribute

progress_token: ProgressToken

The progress token which was given in the initial request, used to associate this notification with the request that is proceeding.

progress instance-attribute

progress: float

The progress thus far. This should increase every time progress is made, even if the total is unknown.

total class-attribute instance-attribute

total: float | None = None

Total number of items to process (or total progress required), if known.

message class-attribute instance-attribute

message: str | None = None

Message related to progress.

This should provide relevant human-readable progress information.

ProgressToken module-attribute

ProgressToken = str | int

A progress token, used to associate progress notifications with the original request.

Prompt

Bases: BaseMetadata

A prompt or prompt template that the server offers.

Source code in src/mcp-types/mcp_types/_types.py

class Prompt(BaseMetadata):
    """A prompt or prompt template that the server offers."""

    description: str | None = None
    """An optional description of what this prompt provides."""
    arguments: list[PromptArgument] | None = None
    """A list of arguments to use for templating the prompt."""
    icons: list[Icon] | None = None
    """An optional list of icons for this prompt."""
    meta: Meta | None = Field(alias="_meta", default=None)
    """
    See [MCP specification](https://github.com/modelcontextprotocol/modelcontextprotocol/blob/47339c03c143bb4ec01a26e721a1b8fe66634ebe/docs/specification/draft/basic/index.mdx#general-fields)
    for notes on _meta usage.
    """

description class-attribute instance-attribute

description: str | None = None

An optional description of what this prompt provides.

arguments class-attribute instance-attribute

arguments: list[PromptArgument] | None = None

A list of arguments to use for templating the prompt.

icons class-attribute instance-attribute

icons: list[Icon] | None = None

An optional list of icons for this prompt.

meta class-attribute instance-attribute

meta: Meta | None = Field(alias='_meta', default=None)

See MCP specification for notes on _meta usage.

PromptArgument

Bases: BaseMetadata

Describes an argument that a prompt can accept.

Source code in src/mcp-types/mcp_types/_types.py

class PromptArgument(BaseMetadata):
    """Describes an argument that a prompt can accept."""

    description: str | None = None
    """A human-readable description of the argument."""
    required: bool | None = None
    """Whether this argument must be provided."""

description class-attribute instance-attribute

description: str | None = None

A human-readable description of the argument.

required class-attribute instance-attribute

required: bool | None = None

Whether this argument must be provided.

PromptListChangedNotification

Bases: Notification[NotificationParams | None, Literal['notifications/prompts/list_changed']]

An optional notification from the server to the client, informing it that the list of prompts it offers has changed.

May be sent spontaneously through 2025-11-25; on 2026-07-28 sessions the client must opt in via subscriptions/listen.

Source code in src/mcp-types/mcp_types/_types.py

class PromptListChangedNotification(
    Notification[NotificationParams | None, Literal["notifications/prompts/list_changed"]]
):
    """An optional notification from the server to the client, informing it that the list
    of prompts it offers has changed.

    May be sent spontaneously through 2025-11-25; on 2026-07-28 sessions the
    client must opt in via `subscriptions/listen`.
    """

    method: Literal["notifications/prompts/list_changed"] = "notifications/prompts/list_changed"
    params: NotificationParams | None = None

PromptMessage

Bases: MCPModel

Describes a message returned as part of a prompt.

Similar to SamplingMessage, but also supports embedded resources.

Source code in src/mcp-types/mcp_types/_types.py

class PromptMessage(MCPModel):
    """Describes a message returned as part of a prompt.

    Similar to `SamplingMessage`, but also supports embedded resources.
    """

    role: Role
    content: ContentBlock

PromptReference

Bases: MCPModel

Identifies a prompt.

Source code in src/mcp-types/mcp_types/_types.py

class PromptReference(MCPModel):
    """Identifies a prompt."""

    type: Literal["ref/prompt"] = "ref/prompt"
    name: str
    """The name of the prompt or prompt template."""
    title: str | None = None
    """Human-readable display title. If not provided, `name` should be used for display."""

name instance-attribute

name: str

The name of the prompt or prompt template.

title class-attribute instance-attribute

title: str | None = None

Human-readable display title. If not provided, name should be used for display.

PromptsCapability

Bases: MCPModel

Capability for prompts operations.

Source code in src/mcp-types/mcp_types/_types.py

class PromptsCapability(MCPModel):
    """Capability for prompts operations."""

    list_changed: bool | None = None
    """Whether this server supports notifications for changes to the prompt list."""

list_changed class-attribute instance-attribute

list_changed: bool | None = None

Whether this server supports notifications for changes to the prompt list.

ReadResourceRequest

Bases: Request[ReadResourceRequestParams, Literal['resources/read']]

Sent from the client to the server, to read a specific resource URI.

Source code in src/mcp-types/mcp_types/_types.py

class ReadResourceRequest(Request[ReadResourceRequestParams, Literal["resources/read"]]):
    """Sent from the client to the server, to read a specific resource URI."""

    method: Literal["resources/read"] = "resources/read"
    params: ReadResourceRequestParams

ReadResourceRequestParams

Bases: InputResponseRequestParams

Source code in src/mcp-types/mcp_types/_types.py

class ReadResourceRequestParams(InputResponseRequestParams):
    uri: str
    """
    The URI of the resource. The URI can use any protocol; it is up to the server
    how to interpret it.
    """

uri instance-attribute

uri: str

The URI of the resource. The URI can use any protocol; it is up to the server how to interpret it.

ReadResourceResult

Bases: CacheableResult

The server's response to a resources/read request from the client.

Source code in src/mcp-types/mcp_types/_types.py

class ReadResourceResult(CacheableResult):
    """The server's response to a resources/read request from the client."""

    contents: list[TextResourceContents | BlobResourceContents]
    """The contents of the resource or sub-resources that were read."""

    result_type: ResultType = "complete"
    """See `ResultType`. Always serialized; older peers ignore it."""

contents instance-attribute

contents: list[TextResourceContents | BlobResourceContents]

The contents of the resource or sub-resources that were read.

result_type class-attribute instance-attribute

result_type: ResultType = 'complete'

See ResultType. Always serialized; older peers ignore it.

RelatedTaskMetadata

Bases: MCPModel

Associates a message with a task, via _meta["io.modelcontextprotocol/related-task"] (2025-11-25 only).

Source code in src/mcp-types/mcp_types/_types.py

class RelatedTaskMetadata(MCPModel):
    """Associates a message with a task, via `_meta["io.modelcontextprotocol/related-task"]` (2025-11-25 only)."""

    task_id: str

Request

Bases: MCPModel, Generic[RequestParamsT, MethodT]

Base class for JSON-RPC requests.

The JSON-RPC envelope (jsonrpc, id) is attached by the session layer (see mcp_types.jsonrpc), not carried here.

Source code in src/mcp-types/mcp_types/_types.py

class Request(MCPModel, Generic[RequestParamsT, MethodT]):
    """Base class for JSON-RPC requests.

    The JSON-RPC envelope (`jsonrpc`, `id`) is attached by the session layer
    (see `mcp_types.jsonrpc`), not carried here.
    """

    method: MethodT
    params: RequestParamsT

RequestParams

Bases: MCPModel

Source code in src/mcp-types/mcp_types/_types.py

class RequestParams(MCPModel):
    meta: RequestParamsMeta | None = Field(alias="_meta", default=None)
    """Metadata reserved by MCP for protocol-level concerns (wire name `_meta`).

    Carries the optional progress token and, on 2026-07-28+ sessions, the
    reserved `io.modelcontextprotocol/*` keys. Required on the wire for
    2026-07-28+ client requests; the session layer supplies the reserved
    entries, so code sending through an SDK session leaves this unset.
    """

meta class-attribute instance-attribute

meta: RequestParamsMeta | None = Field(
    alias="_meta", default=None
)

Metadata reserved by MCP for protocol-level concerns (wire name _meta).

Carries the optional progress token and, on 2026-07-28+ sessions, the reserved io.modelcontextprotocol/* keys. Required on the wire for 2026-07-28+ client requests; the session layer supplies the reserved entries, so code sending through an SDK session leaves this unset.

RequestParamsMeta

Bases: TypedDict

The _meta object on request params (schema name: RequestMetaObject).

An open map: arbitrary keys round-trip via extra_items=Any. Read or set the reserved io.modelcontextprotocol/* keys via the *_META_KEY constants.

Source code in src/mcp-types/mcp_types/_types.py

class RequestParamsMeta(TypedDict, extra_items=Any):
    """The `_meta` object on request params (schema name: `RequestMetaObject`).

    An open map: arbitrary keys round-trip via `extra_items=Any`. Read or set
    the reserved `io.modelcontextprotocol/*` keys via the `*_META_KEY` constants.
    """

    progress_token: NotRequired[ProgressToken]
    """
    If specified, the caller requests out-of-band progress notifications for
    this request (as represented by notifications/progress). The value of this
    parameter is an opaque token that will be attached to any subsequent
    notifications. The receiver is not obligated to provide these notifications.
    """

progress_token instance-attribute

progress_token: NotRequired[ProgressToken]

If specified, the caller requests out-of-band progress notifications for this request (as represented by notifications/progress). The value of this parameter is an opaque token that will be attached to any subsequent notifications. The receiver is not obligated to provide these notifications.

Resource

Bases: BaseMetadata

A known resource that the server is capable of reading.

Source code in src/mcp-types/mcp_types/_types.py

class Resource(BaseMetadata):
    """A known resource that the server is capable of reading."""

    uri: str
    """The URI of this resource."""

    description: str | None = None
    """A description of what this resource represents."""

    mime_type: str | None = None
    """The MIME type of this resource, if known."""

    size: int | None = None
    """The size of the raw resource content, in bytes (i.e., before base64 encoding or any tokenization), if known.

    This can be used by Hosts to display file sizes and estimate context window usage.
    """

    icons: list[Icon] | None = None
    """Optional set of sized icons that the client can display in a user interface."""

    annotations: Annotations | None = None
    """Optional annotations for the client."""

    meta: Meta | None = Field(alias="_meta", default=None)
    """See the MCP specification for notes on `_meta` usage."""

uri instance-attribute

uri: str

The URI of this resource.

description class-attribute instance-attribute

description: str | None = None

A description of what this resource represents.

mime_type class-attribute instance-attribute

mime_type: str | None = None

The MIME type of this resource, if known.

size class-attribute instance-attribute

size: int | None = None

The size of the raw resource content, in bytes (i.e., before base64 encoding or any tokenization), if known.

This can be used by Hosts to display file sizes and estimate context window usage.

icons class-attribute instance-attribute

icons: list[Icon] | None = None

Optional set of sized icons that the client can display in a user interface.

annotations class-attribute instance-attribute

annotations: Annotations | None = None

Optional annotations for the client.

meta class-attribute instance-attribute

meta: Meta | None = Field(alias='_meta', default=None)

See the MCP specification for notes on _meta usage.

ResourceContents

Bases: MCPModel

The contents of a specific resource or sub-resource.

Source code in src/mcp-types/mcp_types/_types.py

class ResourceContents(MCPModel):
    """The contents of a specific resource or sub-resource."""

    uri: str
    """The URI of this resource."""
    mime_type: str | None = None
    """The MIME type of this resource, if known."""
    meta: Meta | None = Field(alias="_meta", default=None)
    """
    See [MCP specification](https://github.com/modelcontextprotocol/modelcontextprotocol/blob/47339c03c143bb4ec01a26e721a1b8fe66634ebe/docs/specification/draft/basic/index.mdx#general-fields)
    for notes on _meta usage.
    """

uri instance-attribute

uri: str

The URI of this resource.

mime_type class-attribute instance-attribute

mime_type: str | None = None

The MIME type of this resource, if known.

meta class-attribute instance-attribute

meta: Meta | None = Field(alias='_meta', default=None)

See MCP specification for notes on _meta usage.

ResourceLink

Bases: Resource

A resource that the server is capable of reading, included in a prompt or tool call result.

Note: resource links returned by tools are not guaranteed to appear in the results of resources/list requests.

Source code in src/mcp-types/mcp_types/_types.py

class ResourceLink(Resource):
    """A resource that the server is capable of reading, included in a prompt or tool call result.

    Note: resource links returned by tools are not guaranteed to appear in the results of `resources/list` requests.
    """

    type: Literal["resource_link"] = "resource_link"

ResourceListChangedNotification

Bases: Notification[NotificationParams | None, Literal['notifications/resources/list_changed']]

An optional notification from the server to the client, informing it that the list of resources it can read from has changed.

May be sent spontaneously through 2025-11-25; on 2026-07-28 sessions the client must opt in via subscriptions/listen.

Source code in src/mcp-types/mcp_types/_types.py

class ResourceListChangedNotification(
    Notification[NotificationParams | None, Literal["notifications/resources/list_changed"]]
):
    """An optional notification from the server to the client, informing it that the list
    of resources it can read from has changed.

    May be sent spontaneously through 2025-11-25; on 2026-07-28 sessions the
    client must opt in via `subscriptions/listen`.
    """

    method: Literal["notifications/resources/list_changed"] = "notifications/resources/list_changed"
    params: NotificationParams | None = None

ResourcesCapability

Bases: MCPModel

Capability for resources operations.

Source code in src/mcp-types/mcp_types/_types.py

class ResourcesCapability(MCPModel):
    """Capability for resources operations."""

    subscribe: bool | None = None
    """Whether this server supports subscribing to resource updates."""
    list_changed: bool | None = None
    """Whether this server supports notifications for changes to the resource list."""

subscribe class-attribute instance-attribute

subscribe: bool | None = None

Whether this server supports subscribing to resource updates.

list_changed class-attribute instance-attribute

list_changed: bool | None = None

Whether this server supports notifications for changes to the resource list.

ResourceTemplate

Bases: BaseMetadata

A template description for resources available on the server.

Source code in src/mcp-types/mcp_types/_types.py

class ResourceTemplate(BaseMetadata):
    """A template description for resources available on the server."""

    uri_template: str
    """A URI template (according to RFC 6570) that can be used to construct resource URIs."""

    description: str | None = None
    """A description of what this template is for."""

    mime_type: str | None = None
    """The MIME type for all resources that match this template.

    This should only be included if all resources matching this template have the same type.
    """

    icons: list[Icon] | None = None
    """An optional set of sized icons that the client can display in a user interface."""

    annotations: Annotations | None = None
    """Optional annotations for the client."""

    meta: Meta | None = Field(alias="_meta", default=None)
    """
    See [MCP specification](https://github.com/modelcontextprotocol/modelcontextprotocol/blob/47339c03c143bb4ec01a26e721a1b8fe66634ebe/docs/specification/draft/basic/index.mdx#general-fields)
    for notes on _meta usage.
    """

uri_template instance-attribute

uri_template: str

A URI template (according to RFC 6570) that can be used to construct resource URIs.

description class-attribute instance-attribute

description: str | None = None

A description of what this template is for.

mime_type class-attribute instance-attribute

mime_type: str | None = None

The MIME type for all resources that match this template.

This should only be included if all resources matching this template have the same type.

icons class-attribute instance-attribute

icons: list[Icon] | None = None

An optional set of sized icons that the client can display in a user interface.

annotations class-attribute instance-attribute

annotations: Annotations | None = None

Optional annotations for the client.

meta class-attribute instance-attribute

meta: Meta | None = Field(alias='_meta', default=None)

See MCP specification for notes on _meta usage.

ResourceTemplateReference

Bases: MCPModel

A reference to a resource or resource template definition.

Source code in src/mcp-types/mcp_types/_types.py

class ResourceTemplateReference(MCPModel):
    """A reference to a resource or resource template definition."""

    type: Literal["ref/resource"] = "ref/resource"
    uri: str
    """The URI or URI template of the resource."""

uri instance-attribute

uri: str

The URI or URI template of the resource.

ResourceUpdatedNotification

Bases: Notification[ResourceUpdatedNotificationParams, Literal['notifications/resources/updated']]

A notification from the server to the client, informing it that a resource has changed and may need to be read again.

Only sent if the client subscribed: via resources/subscribe through 2025-11-25, or subscriptions/listen on 2026-07-28.

Source code in src/mcp-types/mcp_types/_types.py

class ResourceUpdatedNotification(
    Notification[ResourceUpdatedNotificationParams, Literal["notifications/resources/updated"]]
):
    """A notification from the server to the client, informing it that a resource has
    changed and may need to be read again.

    Only sent if the client subscribed: via `resources/subscribe` through
    2025-11-25, or `subscriptions/listen` on 2026-07-28.
    """

    method: Literal["notifications/resources/updated"] = "notifications/resources/updated"
    params: ResourceUpdatedNotificationParams

ResourceUpdatedNotificationParams

Bases: NotificationParams

Source code in src/mcp-types/mcp_types/_types.py

class ResourceUpdatedNotificationParams(NotificationParams):
    uri: str
    """
    The URI of the resource that has been updated. This might be a sub-resource of the
    one that the client actually subscribed to.
    """

uri instance-attribute

uri: str

The URI of the resource that has been updated. This might be a sub-resource of the one that the client actually subscribed to.

Result

Bases: MCPModel

Base class for JSON-RPC results.

result_type is declared per concrete subclass, not here, because defaults differ: most results default to "complete", EmptyResult defaults to None (so it dumps as {}; some peer SDKs strict-validate empty results), and InputRequiredResult carries a literal.

Source code in src/mcp-types/mcp_types/_types.py

class Result(MCPModel):
    """Base class for JSON-RPC results.

    `result_type` is declared per concrete subclass, not here, because defaults
    differ: most results default to "complete", `EmptyResult` defaults to None
    (so it dumps as `{}`; some peer SDKs strict-validate empty results), and
    `InputRequiredResult` carries a literal.
    """

    meta: Meta | None = Field(alias="_meta", default=None)
    """
    See [MCP specification](https://github.com/modelcontextprotocol/modelcontextprotocol/blob/47339c03c143bb4ec01a26e721a1b8fe66634ebe/docs/specification/draft/basic/index.mdx#general-fields)
    for notes on _meta usage.
    """

meta class-attribute instance-attribute

meta: Meta | None = Field(alias='_meta', default=None)

See MCP specification for notes on _meta usage.

ResultType module-attribute

ResultType = Literal['complete', 'input_required'] | str

Tags a Result so the client knows how to parse it (2026-07-28).

"complete" means the result is final; "input_required" means it is an InputRequiredResult. The union is open (the tasks extension reserves "task"). Absent resultType is equivalent to "complete".

Role module-attribute

Role = Literal['user', 'assistant']

The sender or recipient of messages and data in a conversation.

Root

Bases: MCPModel

Represents a root directory or file that the server can operate on.

Deprecated in 2026-07-28 (SEP-2577) with the rest of roots.

Source code in src/mcp-types/mcp_types/_types.py

class Root(MCPModel):
    """Represents a root directory or file that the server can operate on.

    Deprecated in 2026-07-28 (SEP-2577) with the rest of roots.
    """

    uri: FileUrl
    """
    The URI identifying the root. This *must* start with file:// for now.
    This restriction may be relaxed in future versions of the protocol to allow
    other URI schemes.
    """
    name: str | None = None
    """
    An optional name for the root. This can be used to provide a human-readable
    identifier for the root, which may be useful for display purposes or for
    referencing the root in other parts of the application.
    """
    meta: Meta | None = Field(alias="_meta", default=None)
    """
    See [MCP specification](https://github.com/modelcontextprotocol/modelcontextprotocol/blob/47339c03c143bb4ec01a26e721a1b8fe66634ebe/docs/specification/draft/basic/index.mdx#general-fields)
    for notes on _meta usage.
    """

uri instance-attribute

uri: FileUrl

The URI identifying the root. This must start with file:// for now. This restriction may be relaxed in future versions of the protocol to allow other URI schemes.

name class-attribute instance-attribute

name: str | None = None

An optional name for the root. This can be used to provide a human-readable identifier for the root, which may be useful for display purposes or for referencing the root in other parts of the application.

meta class-attribute instance-attribute

meta: Meta | None = Field(alias='_meta', default=None)

See MCP specification for notes on _meta usage.

RootsCapability

Bases: MCPModel

Capability for root operations.

Deprecated in protocol 2026-07-28 (SEP-2577) but still carried there as an empty object (list_changed exists only through 2025-11-25).

Source code in src/mcp-types/mcp_types/_types.py

class RootsCapability(MCPModel):
    """Capability for root operations.

    Deprecated in protocol 2026-07-28 (SEP-2577) but still carried there as an
    empty object (`list_changed` exists only through 2025-11-25).
    """

    list_changed: bool | None = None
    """Whether the client supports notifications for changes to the roots list."""

list_changed class-attribute instance-attribute

list_changed: bool | None = None

Whether the client supports notifications for changes to the roots list.

RootsListChangedNotification

Bases: Notification[NotificationParams | None, Literal['notifications/roots/list_changed']]

A notification from the client to the server, informing it that the list of roots has changed.

This notification should be sent whenever the client adds, removes, or modifies any root. The server should then request an updated list of roots using the ListRootsRequest.

Removed in protocol 2026-07-28; sent/received on sessions negotiating <= 2025-11-25.

Source code in src/mcp-types/mcp_types/_types.py

class RootsListChangedNotification(
    Notification[NotificationParams | None, Literal["notifications/roots/list_changed"]]
):
    """A notification from the client to the server, informing it that the list of
    roots has changed.

    This notification should be sent whenever the client adds, removes, or
    modifies any root. The server should then request an updated list of roots
    using the ListRootsRequest.

    Removed in protocol 2026-07-28; sent/received on sessions negotiating <= 2025-11-25.
    """

    method: Literal["notifications/roots/list_changed"] = "notifications/roots/list_changed"
    params: NotificationParams | None = None

SamplingCapability

Bases: MCPModel

Sampling capability structure. Deprecated in 2026-07-28 (SEP-2577); shape unchanged.

Source code in src/mcp-types/mcp_types/_types.py

class SamplingCapability(MCPModel):
    """Sampling capability structure. Deprecated in 2026-07-28 (SEP-2577); shape unchanged."""

    context: SamplingContextCapability | None = None
    """
    Present if the client supports non-'none' values for includeContext parameter.
    SOFT-DEPRECATED: New implementations should use tools parameter instead.
    """
    tools: SamplingToolsCapability | None = None
    """
    Present if the client supports tools and toolChoice parameters in sampling requests.
    Presence indicates full tool calling support during sampling.
    """

context class-attribute instance-attribute

context: SamplingContextCapability | None = None

Present if the client supports non-'none' values for includeContext parameter. SOFT-DEPRECATED: New implementations should use tools parameter instead.

tools class-attribute instance-attribute

tools: SamplingToolsCapability | None = None

Present if the client supports tools and toolChoice parameters in sampling requests. Presence indicates full tool calling support during sampling.

SamplingContent module-attribute

SamplingContent: TypeAlias = (
    TextContent | ImageContent | AudioContent
)

Basic content types for sampling responses (without tool use).

Used for backwards-compatible CreateMessageResult when tools are not used.

SamplingContextCapability

Bases: MCPModel

Capability for context inclusion during sampling.

Indicates support for non-'none' values in the includeContext parameter. SOFT-DEPRECATED: New implementations should use tools parameter instead.

Source code in src/mcp-types/mcp_types/_types.py

class SamplingContextCapability(MCPModel):
    """Capability for context inclusion during sampling.

    Indicates support for non-'none' values in the includeContext parameter.
    SOFT-DEPRECATED: New implementations should use tools parameter instead.
    """

SamplingMessage

Bases: MCPModel

Describes a message issued to or received from an LLM API.

Source code in src/mcp-types/mcp_types/_types.py

class SamplingMessage(MCPModel):
    """Describes a message issued to or received from an LLM API."""

    role: Role
    content: SamplingMessageContentBlock | list[SamplingMessageContentBlock]
    """
    Message content. Can be a single content block or an array of content blocks
    for multi-modal messages and tool interactions.
    """
    meta: Meta | None = Field(alias="_meta", default=None)
    """
    See [MCP specification](https://github.com/modelcontextprotocol/modelcontextprotocol/blob/47339c03c143bb4ec01a26e721a1b8fe66634ebe/docs/specification/draft/basic/index.mdx#general-fields)
    for notes on _meta usage.
    """

    @property
    def content_as_list(self) -> list[SamplingMessageContentBlock]:
        """Returns the content as a list of content blocks, regardless of whether
        it was originally a single block or a list."""
        return self.content if isinstance(self.content, list) else [self.content]

content instance-attribute

content: (
    SamplingMessageContentBlock
    | list[SamplingMessageContentBlock]
)

Message content. Can be a single content block or an array of content blocks for multi-modal messages and tool interactions.

meta class-attribute instance-attribute

meta: Meta | None = Field(alias='_meta', default=None)

See MCP specification for notes on _meta usage.

content_as_list property

content_as_list: list[SamplingMessageContentBlock]

Returns the content as a list of content blocks, regardless of whether it was originally a single block or a list.

SamplingMessageContentBlock module-attribute

SamplingMessageContentBlock: TypeAlias = (
    TextContent
    | ImageContent
    | AudioContent
    | ToolUseContent
    | ToolResultContent
)

Content block types allowed in sampling messages.

This is the widest (2025-11-25+) membership; older sessions allow only a subset on the wire. Serialization never narrows a value to fit; version gating is the session layer's responsibility. Deprecated in 2026-07-28 (SEP-2577).

SamplingToolsCapability

Bases: MCPModel

Capability indicating support for tool calling during sampling.

When present in ClientCapabilities.sampling, indicates that the client supports the tools and toolChoice parameters in sampling requests.

Source code in src/mcp-types/mcp_types/_types.py

class SamplingToolsCapability(MCPModel):
    """Capability indicating support for tool calling during sampling.

    When present in ClientCapabilities.sampling, indicates that the client
    supports the tools and toolChoice parameters in sampling requests.
    """

ServerCapabilities

Bases: MCPModel

Capabilities that a server may support. Not a closed set.

Source code in src/mcp-types/mcp_types/_types.py

class ServerCapabilities(MCPModel):
    """Capabilities that a server may support. Not a closed set."""

    experimental: dict[str, dict[str, Any]] | None = None
    """Experimental, non-standard capabilities that the server supports."""

    logging: LoggingCapability | None = None
    """Present if the server supports sending log messages to the client.
    Deprecated in 2026-07-28 (SEP-2577)."""

    prompts: PromptsCapability | None = None
    """Present if the server offers any prompt templates."""

    resources: ResourcesCapability | None = None
    """Present if the server offers any resources to read."""

    tools: ToolsCapability | None = None
    """Present if the server offers any tools to call."""

    completions: CompletionsCapability | None = None
    """Present if the server offers autocompletion suggestions for prompts and resources."""

    extensions: dict[str, dict[str, Any]] | None = None
    """MCP extensions the server supports (2026-07-28). Keys are extension
    identifiers; values are per-extension settings (empty object = no settings)."""

    tasks: ServerTasksCapability | None = None
    """Present if the server supports task-augmented requests (2025-11-25 only)."""

experimental class-attribute instance-attribute

experimental: dict[str, dict[str, Any]] | None = None

Experimental, non-standard capabilities that the server supports.

logging class-attribute instance-attribute

logging: LoggingCapability | None = None

Present if the server supports sending log messages to the client. Deprecated in 2026-07-28 (SEP-2577).

prompts class-attribute instance-attribute

prompts: PromptsCapability | None = None

Present if the server offers any prompt templates.

resources class-attribute instance-attribute

resources: ResourcesCapability | None = None

Present if the server offers any resources to read.

tools class-attribute instance-attribute

tools: ToolsCapability | None = None

Present if the server offers any tools to call.

completions class-attribute instance-attribute

completions: CompletionsCapability | None = None

Present if the server offers autocompletion suggestions for prompts and resources.

extensions class-attribute instance-attribute

extensions: dict[str, dict[str, Any]] | None = None

MCP extensions the server supports (2026-07-28). Keys are extension identifiers; values are per-extension settings (empty object = no settings).

tasks class-attribute instance-attribute

tasks: ServerTasksCapability | None = None

Present if the server supports task-augmented requests (2025-11-25 only).

ServerNotification module-attribute

ServerNotification = (
    CancelledNotification
    | ProgressNotification
    | LoggingMessageNotification
    | ResourceUpdatedNotification
    | ResourceListChangedNotification
    | ToolListChangedNotification
    | PromptListChangedNotification
    | ElicitCompleteNotification
    | SubscriptionsAcknowledgedNotification
)

Union of server-to-client notification payloads across all supported protocol versions.

TaskStatusNotification is deliberately excluded (types-only).

ServerRequest module-attribute

ServerRequest = (
    PingRequest
    | CreateMessageRequest
    | ListRootsRequest
    | ElicitRequest
)

Union of standalone JSON-RPC requests a server can send to a client.

Live through 2025-11-25 only: 2026-07-28 has no server-to-client JSON-RPC requests (these payloads are embedded in InputRequiredResult instead).

ServerResult module-attribute

ServerResult = (
    EmptyResult
    | InitializeResult
    | DiscoverResult
    | CompleteResult
    | GetPromptResult
    | ListPromptsResult
    | ListResourcesResult
    | ListResourceTemplatesResult
    | ReadResourceResult
    | CallToolResult
    | ListToolsResult
    | SubscriptionsListenResult
    | InputRequiredResult
)

Union of every result payload a server can return for a client request.

InputRequiredResult is deliberately last: both of its fields are optional, so an earlier position would shadow other members during union resolution.

ServerTasksCapability

Bases: MCPModel

Capability for server tasks operations (2025-11-25 only).

Source code in src/mcp-types/mcp_types/_types.py

class ServerTasksCapability(MCPModel):
    """Capability for server tasks operations (2025-11-25 only)."""

    list: TasksListCapability | None = None
    cancel: TasksCancelCapability | None = None
    requests: ServerTasksRequestsCapability | None = None

ServerTasksRequestsCapability

Bases: MCPModel

Specifies which request types the server can augment with tasks (2025-11-25 only).

Source code in src/mcp-types/mcp_types/_types.py

class ServerTasksRequestsCapability(MCPModel):
    """Specifies which request types the server can augment with tasks (2025-11-25 only)."""

    tools: TasksToolsCapability | None = None

SetLevelRequest

Bases: Request[SetLevelRequestParams, Literal['logging/setLevel']]

A request from the client to the server, to enable or adjust logging.

Removed in protocol 2026-07-28; sent/received on sessions negotiating <= 2025-11-25. On 2026-07-28 the client opts in per-request via _meta (LOG_LEVEL_META_KEY).

Source code in src/mcp-types/mcp_types/_types.py

class SetLevelRequest(Request[SetLevelRequestParams, Literal["logging/setLevel"]]):
    """A request from the client to the server, to enable or adjust logging.

    Removed in protocol 2026-07-28; sent/received on sessions negotiating <= 2025-11-25.
    On 2026-07-28 the client opts in per-request via `_meta` (`LOG_LEVEL_META_KEY`).
    """

    method: Literal["logging/setLevel"] = "logging/setLevel"
    params: SetLevelRequestParams

SetLevelRequestParams

Bases: RequestParams

Parameters for setting the logging level.

Removed in protocol 2026-07-28; sent/received on sessions negotiating <= 2025-11-25.

Source code in src/mcp-types/mcp_types/_types.py

class SetLevelRequestParams(RequestParams):
    """Parameters for setting the logging level.

    Removed in protocol 2026-07-28; sent/received on sessions negotiating <= 2025-11-25.
    """

    level: LoggingLevel
    """The level of logging that the client wants to receive from the server.
    The server should send all logs at this level and higher (more severe)."""

level instance-attribute

level: LoggingLevel

The level of logging that the client wants to receive from the server. The server should send all logs at this level and higher (more severe).

StopReason module-attribute

StopReason = (
    Literal[
        "endTurn", "stopSequence", "maxTokens", "toolUse"
    ]
    | str
)

The reason why sampling stopped, if known.

An open union to allow provider-specific stop reasons. "toolUse" is 2025-11-25+.

SubscribeRequest

Bases: Request[SubscribeRequestParams, Literal['resources/subscribe']]

Sent from the client to request resources/updated notifications from the server whenever a particular resource changes.

Removed in protocol 2026-07-28; sent/received on sessions negotiating <= 2025-11-25. On 2026-07-28 use subscriptions/listen instead.

Source code in src/mcp-types/mcp_types/_types.py

class SubscribeRequest(Request[SubscribeRequestParams, Literal["resources/subscribe"]]):
    """Sent from the client to request resources/updated notifications from the server
    whenever a particular resource changes.

    Removed in protocol 2026-07-28; sent/received on sessions negotiating <= 2025-11-25.
    On 2026-07-28 use `subscriptions/listen` instead.
    """

    method: Literal["resources/subscribe"] = "resources/subscribe"
    params: SubscribeRequestParams

SubscribeRequestParams

Bases: RequestParams

Parameters for subscribing to a resource.

Removed in protocol 2026-07-28; sent/received on sessions negotiating <= 2025-11-25.

Source code in src/mcp-types/mcp_types/_types.py

class SubscribeRequestParams(RequestParams):
    """Parameters for subscribing to a resource.

    Removed in protocol 2026-07-28; sent/received on sessions negotiating <= 2025-11-25.
    """

    uri: str
    """
    The URI of the resource to subscribe to. The URI can use any protocol; it is up to
    the server how to interpret it.
    """

uri instance-attribute

uri: str

The URI of the resource to subscribe to. The URI can use any protocol; it is up to the server how to interpret it.

SubscriptionFilter

Bases: MCPModel

The set of notification types a client opts in to via subscriptions/listen (2026-07-28).

Each type is opt-in; the server MUST NOT send types not requested here. Echoed back in notifications/subscriptions/acknowledged as the subset the server agreed to honor. Extensions merge additional keys (e.g. taskIds), so unknown keys round-trip.

Source code in src/mcp-types/mcp_types/_types.py

class SubscriptionFilter(MCPModel):
    """The set of notification types a client opts in to via `subscriptions/listen` (2026-07-28).

    Each type is opt-in; the server MUST NOT send types not requested here.
    Echoed back in `notifications/subscriptions/acknowledged` as the subset the
    server agreed to honor. Extensions merge additional keys (e.g. `taskIds`),
    so unknown keys round-trip.
    """

    model_config = ConfigDict(alias_generator=to_camel, populate_by_name=True, extra="allow")

    tools_list_changed: bool | None = None
    """If true, receive notifications/tools/list_changed."""

    prompts_list_changed: bool | None = None
    """If true, receive notifications/prompts/list_changed."""

    resources_list_changed: bool | None = None
    """If true, receive notifications/resources/list_changed."""

    resource_subscriptions: list[str] | None = None
    """Subscribe to notifications/resources/updated for these resource URIs."""

tools_list_changed class-attribute instance-attribute

tools_list_changed: bool | None = None

If true, receive notifications/tools/list_changed.

prompts_list_changed class-attribute instance-attribute

prompts_list_changed: bool | None = None

If true, receive notifications/prompts/list_changed.

resources_list_changed class-attribute instance-attribute

resources_list_changed: bool | None = None

If true, receive notifications/resources/list_changed.

resource_subscriptions class-attribute instance-attribute

resource_subscriptions: list[str] | None = None

Subscribe to notifications/resources/updated for these resource URIs.

SubscriptionsAcknowledgedNotification

Bases: Notification[SubscriptionsAcknowledgedNotificationParams, Literal['notifications/subscriptions/acknowledged']]

First message on a subscriptions/listen stream: acknowledges the subscription and reports which notification types the server will honor (2026-07-28).

Source code in src/mcp-types/mcp_types/_types.py

class SubscriptionsAcknowledgedNotification(
    Notification[
        SubscriptionsAcknowledgedNotificationParams,
        Literal["notifications/subscriptions/acknowledged"],
    ]
):
    """First message on a `subscriptions/listen` stream: acknowledges the
    subscription and reports which notification types the server will honor (2026-07-28).
    """

    method: Literal["notifications/subscriptions/acknowledged"] = "notifications/subscriptions/acknowledged"
    params: SubscriptionsAcknowledgedNotificationParams

SubscriptionsAcknowledgedNotificationParams

Bases: NotificationParams

Source code in src/mcp-types/mcp_types/_types.py

class SubscriptionsAcknowledgedNotificationParams(NotificationParams):
    notifications: SubscriptionFilter
    """The subset of requested notification types the server agreed to honor.
    Unsupported types are omitted."""

notifications instance-attribute

notifications: SubscriptionFilter

The subset of requested notification types the server agreed to honor. Unsupported types are omitted.

SubscriptionsListenRequest

Bases: Request[SubscriptionsListenRequestParams, Literal['subscriptions/listen']]

Opens a long-lived channel for receiving notifications outside the context of a specific request (2026-07-28).

Source code in src/mcp-types/mcp_types/_types.py

class SubscriptionsListenRequest(Request[SubscriptionsListenRequestParams, Literal["subscriptions/listen"]]):
    """Opens a long-lived channel for receiving notifications outside the context
    of a specific request (2026-07-28).
    """

    method: Literal["subscriptions/listen"] = "subscriptions/listen"
    params: SubscriptionsListenRequestParams

SubscriptionsListenRequestParams

Bases: RequestParams

Source code in src/mcp-types/mcp_types/_types.py

class SubscriptionsListenRequestParams(RequestParams):
    notifications: SubscriptionFilter
    """The notifications the client opts in to on this stream."""

notifications instance-attribute

notifications: SubscriptionFilter

The notifications the client opts in to on this stream.

SubscriptionsListenResult

Bases: Result

Signals that a subscriptions/listen stream has ended gracefully (2026-07-28).

Because the listen stream is long-lived, this result is sent only when the server tears the subscription down (for example during shutdown); an abrupt transport close carries no response. The body is otherwise empty: the _meta["io.modelcontextprotocol/subscriptionId"] key is required on the wire and equals the JSON-RPC id of the originating subscriptions/listen request.

Source code in src/mcp-types/mcp_types/_types.py

class SubscriptionsListenResult(Result):
    """Signals that a `subscriptions/listen` stream has ended gracefully (2026-07-28).

    Because the listen stream is long-lived, this result is sent only when the
    server tears the subscription down (for example during shutdown); an abrupt
    transport close carries no response. The body is otherwise empty: the
    `_meta["io.modelcontextprotocol/subscriptionId"]` key is required on the
    wire and equals the JSON-RPC id of the originating `subscriptions/listen`
    request.
    """

    result_type: ResultType = "complete"
    """See `ResultType`. Always serialized; older peers ignore it."""

result_type class-attribute instance-attribute

result_type: ResultType = 'complete'

See ResultType. Always serialized; older peers ignore it.

Task

Bases: MCPModel

Data associated with a task (2025-11-25 only).

Source code in src/mcp-types/mcp_types/_types.py

class Task(MCPModel):
    """Data associated with a task (2025-11-25 only)."""

    task_id: str

    status: TaskStatus

    status_message: str | None = None
    """Optional human-readable message describing the current task state."""

    created_at: str
    """ISO 8601 timestamp when the task was created."""

    last_updated_at: str
    """ISO 8601 timestamp when the task was last updated."""

    ttl: int | None
    """Actual retention duration from creation in milliseconds, null for unlimited."""

    poll_interval: int | None = None
    """Suggested polling interval in milliseconds."""

status_message class-attribute instance-attribute

status_message: str | None = None

Optional human-readable message describing the current task state.

created_at instance-attribute

created_at: str

ISO 8601 timestamp when the task was created.

last_updated_at instance-attribute

last_updated_at: str

ISO 8601 timestamp when the task was last updated.

ttl instance-attribute

ttl: int | None

Actual retention duration from creation in milliseconds, null for unlimited.

poll_interval class-attribute instance-attribute

poll_interval: int | None = None

Suggested polling interval in milliseconds.

TaskMetadata

Bases: MCPModel

Metadata for augmenting a request with task execution (the task params field; 2025-11-25 only).

Source code in src/mcp-types/mcp_types/_types.py

class TaskMetadata(MCPModel):
    """Metadata for augmenting a request with task execution (the `task` params field; 2025-11-25 only)."""

    ttl: int | None = None
    """Requested duration in milliseconds to retain task from creation."""

ttl class-attribute instance-attribute

ttl: int | None = None

Requested duration in milliseconds to retain task from creation.

TasksCallCapability

Bases: MCPModel

Capability for task-augmented tools/call requests (2025-11-25 only).

Source code in src/mcp-types/mcp_types/_types.py

class TasksCallCapability(MCPModel):
    """Capability for task-augmented tools/call requests (2025-11-25 only)."""

TasksCancelCapability

Bases: MCPModel

Capability for tasks cancel operations (2025-11-25 only).

Source code in src/mcp-types/mcp_types/_types.py

class TasksCancelCapability(MCPModel):
    """Capability for tasks cancel operations (2025-11-25 only)."""

TasksCreateElicitationCapability

Bases: MCPModel

Capability for task-augmented elicitation/create requests (2025-11-25 only).

Source code in src/mcp-types/mcp_types/_types.py

class TasksCreateElicitationCapability(MCPModel):
    """Capability for task-augmented elicitation/create requests (2025-11-25 only)."""

TasksCreateMessageCapability

Bases: MCPModel

Capability for task-augmented sampling/createMessage requests (2025-11-25 only).

Source code in src/mcp-types/mcp_types/_types.py

class TasksCreateMessageCapability(MCPModel):
    """Capability for task-augmented sampling/createMessage requests (2025-11-25 only)."""

TasksElicitationCapability

Bases: MCPModel

Capability for task-augmented elicitation operations (2025-11-25 only).

Source code in src/mcp-types/mcp_types/_types.py

class TasksElicitationCapability(MCPModel):
    """Capability for task-augmented elicitation operations (2025-11-25 only)."""

    create: TasksCreateElicitationCapability | None = None

TasksListCapability

Bases: MCPModel

Capability for tasks listing operations (2025-11-25 only).

Source code in src/mcp-types/mcp_types/_types.py

class TasksListCapability(MCPModel):
    """Capability for tasks listing operations (2025-11-25 only)."""

TasksSamplingCapability

Bases: MCPModel

Capability for task-augmented sampling operations (2025-11-25 only).

Source code in src/mcp-types/mcp_types/_types.py

class TasksSamplingCapability(MCPModel):
    """Capability for task-augmented sampling operations (2025-11-25 only)."""

    create_message: TasksCreateMessageCapability | None = None

TaskStatus module-attribute

TaskStatus = Literal[
    "working",
    "input_required",
    "completed",
    "failed",
    "cancelled",
]

The status of a task (2025-11-25 only).

TaskStatusNotification

Bases: Notification[TaskStatusNotificationParams, Literal['notifications/tasks/status']]

An optional notification informing the requestor that a task's status has changed (2025-11-25 only).

Source code in src/mcp-types/mcp_types/_types.py

class TaskStatusNotification(Notification[TaskStatusNotificationParams, Literal["notifications/tasks/status"]]):
    """An optional notification informing the requestor that a task's status has changed (2025-11-25 only)."""

    method: Literal["notifications/tasks/status"] = "notifications/tasks/status"
    params: TaskStatusNotificationParams

TaskStatusNotificationParams

Bases: NotificationParams, Task

Parameters for a notifications/tasks/status notification.

Source code in src/mcp-types/mcp_types/_types.py

class TaskStatusNotificationParams(NotificationParams, Task):
    """Parameters for a `notifications/tasks/status` notification."""

TasksToolsCapability

Bases: MCPModel

Capability for task-augmented tool operations (2025-11-25 only).

Source code in src/mcp-types/mcp_types/_types.py

class TasksToolsCapability(MCPModel):
    """Capability for task-augmented tool operations (2025-11-25 only)."""

    call: TasksCallCapability | None = None

TextContent

Bases: MCPModel

Text provided to or from an LLM.

Source code in src/mcp-types/mcp_types/_types.py

class TextContent(MCPModel):
    """Text provided to or from an LLM."""

    type: Literal["text"] = "text"
    text: str
    """The text content of the message."""
    annotations: Annotations | None = None
    """Optional annotations for the client."""
    meta: Meta | None = Field(alias="_meta", default=None)
    """
    See [MCP specification](https://github.com/modelcontextprotocol/modelcontextprotocol/blob/47339c03c143bb4ec01a26e721a1b8fe66634ebe/docs/specification/draft/basic/index.mdx#general-fields)
    for notes on _meta usage.
    """

text instance-attribute

text: str

The text content of the message.

annotations class-attribute instance-attribute

annotations: Annotations | None = None

Optional annotations for the client.

meta class-attribute instance-attribute

meta: Meta | None = Field(alias='_meta', default=None)

See MCP specification for notes on _meta usage.

TextResourceContents

Bases: ResourceContents

Text contents of a resource.

Source code in src/mcp-types/mcp_types/_types.py

class TextResourceContents(ResourceContents):
    """Text contents of a resource."""

    text: str
    """
    The text of the item. This must only be set if the item can actually be represented
    as text (not binary data).
    """

text instance-attribute

text: str

The text of the item. This must only be set if the item can actually be represented as text (not binary data).

Tool

Bases: BaseMetadata

Definition for a tool the client can call.

Source code in src/mcp-types/mcp_types/_types.py

class Tool(BaseMetadata):
    """Definition for a tool the client can call."""

    description: str | None = None
    """A human-readable description of the tool."""
    input_schema: dict[str, Any]
    """A JSON Schema object defining the expected parameters for the tool.

    `type: "object"` is required at the root. 2026-07-28 allows any JSON Schema
    2020-12 keyword; earlier versions define only `type`/`properties`/`required`.
    """
    execution: ToolExecution | None = None
    """Execution-related properties (2025-11-25 only; removed in 2026-07-28)."""
    output_schema: dict[str, Any] | None = None
    """An optional JSON Schema object defining the structure of the tool's output
    returned in the `structured_content` field of a `CallToolResult`.

    Restricted to `type: "object"` at the root through 2025-11-25; any valid
    JSON Schema 2020-12 on 2026-07-28.
    """
    icons: list[Icon] | None = None
    """Optional set of sized icons for display (2025-11-25+)."""
    annotations: ToolAnnotations | None = None
    """Optional additional tool information.
    Display-name precedence: `title`, `annotations.title`, then `name`."""
    meta: Meta | None = Field(alias="_meta", default=None)
    """See the MCP specification for notes on `_meta` usage."""

description class-attribute instance-attribute

description: str | None = None

A human-readable description of the tool.

input_schema instance-attribute

input_schema: dict[str, Any]

A JSON Schema object defining the expected parameters for the tool.

type: "object" is required at the root. 2026-07-28 allows any JSON Schema 2020-12 keyword; earlier versions define only type/properties/required.

execution class-attribute instance-attribute

execution: ToolExecution | None = None

Execution-related properties (2025-11-25 only; removed in 2026-07-28).

output_schema class-attribute instance-attribute

output_schema: dict[str, Any] | None = None

An optional JSON Schema object defining the structure of the tool's output returned in the structured_content field of a CallToolResult.

Restricted to type: "object" at the root through 2025-11-25; any valid JSON Schema 2020-12 on 2026-07-28.

icons class-attribute instance-attribute

icons: list[Icon] | None = None

Optional set of sized icons for display (2025-11-25+).

annotations class-attribute instance-attribute

annotations: ToolAnnotations | None = None

Optional additional tool information. Display-name precedence: title, annotations.title, then name.

meta class-attribute instance-attribute

meta: Meta | None = Field(alias='_meta', default=None)

See the MCP specification for notes on _meta usage.

ToolAnnotations

Bases: MCPModel

Additional properties describing a Tool to clients.

NOTE: all properties in ToolAnnotations are hints. They are not guaranteed to provide a faithful description of tool behavior (including descriptive properties like title).

Clients should never make tool use decisions based on ToolAnnotations received from untrusted servers.

Source code in src/mcp-types/mcp_types/_types.py

class ToolAnnotations(MCPModel):
    """Additional properties describing a Tool to clients.

    NOTE: all properties in ToolAnnotations are **hints**.
    They are not guaranteed to provide a faithful description of
    tool behavior (including descriptive properties like `title`).

    Clients should never make tool use decisions based on ToolAnnotations
    received from untrusted servers.
    """

    title: str | None = None
    """A human-readable title for the tool."""

    read_only_hint: bool | None = None
    """
    If true, the tool does not modify its environment.
    Default: false
    """

    destructive_hint: bool | None = None
    """
    If true, the tool may perform destructive updates to its environment.
    If false, the tool performs only additive updates.
    (This property is meaningful only when `read_only_hint == false`)
    Default: true
    """

    idempotent_hint: bool | None = None
    """
    If true, calling the tool repeatedly with the same arguments
    will have no additional effect on its environment.
    (This property is meaningful only when `read_only_hint == false`)
    Default: false
    """

    open_world_hint: bool | None = None
    """
    If true, this tool may interact with an "open world" of external
    entities. If false, the tool's domain of interaction is closed.
    For example, the world of a web search tool is open, whereas that
    of a memory tool is not.
    Default: true
    """

title class-attribute instance-attribute

title: str | None = None

A human-readable title for the tool.

read_only_hint class-attribute instance-attribute

read_only_hint: bool | None = None

If true, the tool does not modify its environment. Default: false

destructive_hint class-attribute instance-attribute

destructive_hint: bool | None = None

If true, the tool may perform destructive updates to its environment. If false, the tool performs only additive updates. (This property is meaningful only when read_only_hint == false) Default: true

idempotent_hint class-attribute instance-attribute

idempotent_hint: bool | None = None

If true, calling the tool repeatedly with the same arguments will have no additional effect on its environment. (This property is meaningful only when read_only_hint == false) Default: false

open_world_hint class-attribute instance-attribute

open_world_hint: bool | None = None

If true, this tool may interact with an "open world" of external entities. If false, the tool's domain of interaction is closed. For example, the world of a web search tool is open, whereas that of a memory tool is not. Default: true

ToolChoice

Bases: MCPModel

Controls tool selection behavior for sampling requests (2025-11-25+).

The client MUST return an error if this is received without the sampling.tools capability. Absent means {"mode": "auto"}.

Source code in src/mcp-types/mcp_types/_types.py

class ToolChoice(MCPModel):
    """Controls tool selection behavior for sampling requests (2025-11-25+).

    The client MUST return an error if this is received without the
    `sampling.tools` capability. Absent means `{"mode": "auto"}`.
    """

    mode: Literal["auto", "required", "none"] | None = None
    """
    Controls the tool use ability of the model:
    - "auto": Model decides whether to use tools (default)
    - "required": Model MUST use at least one tool before completing
    - "none": Model MUST NOT use any tools
    """

mode class-attribute instance-attribute

mode: Literal['auto', 'required', 'none'] | None = None

Controls the tool use ability of the model: - "auto": Model decides whether to use tools (default) - "required": Model MUST use at least one tool before completing - "none": Model MUST NOT use any tools

ToolExecution

Bases: MCPModel

Execution-related properties for a tool (2025-11-25 only).

Source code in src/mcp-types/mcp_types/_types.py

class ToolExecution(MCPModel):
    """Execution-related properties for a tool (2025-11-25 only)."""

    task_support: Literal["forbidden", "optional", "required"] | None = None
    """Whether this tool supports task-augmented execution. Absent means "forbidden"."""

task_support class-attribute instance-attribute

task_support: (
    Literal["forbidden", "optional", "required"] | None
) = None

Whether this tool supports task-augmented execution. Absent means "forbidden".

ToolListChangedNotification

Bases: Notification[NotificationParams | None, Literal['notifications/tools/list_changed']]

An optional notification from the server to the client, informing it that the list of tools it offers has changed.

May be sent spontaneously through 2025-11-25; on 2026-07-28 sessions the client must opt in via subscriptions/listen.

Source code in src/mcp-types/mcp_types/_types.py

class ToolListChangedNotification(Notification[NotificationParams | None, Literal["notifications/tools/list_changed"]]):
    """An optional notification from the server to the client, informing it that the list
    of tools it offers has changed.

    May be sent spontaneously through 2025-11-25; on 2026-07-28 sessions the
    client must opt in via `subscriptions/listen`.
    """

    method: Literal["notifications/tools/list_changed"] = "notifications/tools/list_changed"
    params: NotificationParams | None = None

ToolResultContent

Bases: MCPModel

The result of a tool use, provided by the user back to the assistant (2025-11-25+).

Appears in sampling messages as a response to a ToolUseContent block. Requires the sampling.tools client capability. Deprecated in 2026-07-28 (SEP-2577).

Source code in src/mcp-types/mcp_types/_types.py

class ToolResultContent(MCPModel):
    """The result of a tool use, provided by the user back to the assistant (2025-11-25+).

    Appears in sampling messages as a response to a `ToolUseContent` block.
    Requires the `sampling.tools` client capability. Deprecated in 2026-07-28 (SEP-2577).
    """

    type: Literal["tool_result"] = "tool_result"
    """Discriminator for tool result content."""

    tool_use_id: str
    """The `id` of the `ToolUseContent` this result corresponds to."""

    content: list[ContentBlock] = []
    """The unstructured result content (same format as `CallToolResult.content`)."""

    structured_content: Any = None
    """An optional structured result value. Any JSON value on 2026-07-28;
    restricted to a JSON object on 2025-11-25."""

    is_error: bool | None = None
    """Whether the tool use resulted in an error. Absent is equivalent to false."""

    meta: Meta | None = Field(alias="_meta", default=None)
    """Optional metadata. Clients SHOULD preserve this in subsequent sampling
    requests to enable caching optimizations."""

type class-attribute instance-attribute

type: Literal['tool_result'] = 'tool_result'

Discriminator for tool result content.

tool_use_id instance-attribute

tool_use_id: str

The id of the ToolUseContent this result corresponds to.

content class-attribute instance-attribute

content: list[ContentBlock] = []

The unstructured result content (same format as CallToolResult.content).

structured_content class-attribute instance-attribute

structured_content: Any = None

An optional structured result value. Any JSON value on 2026-07-28; restricted to a JSON object on 2025-11-25.

is_error class-attribute instance-attribute

is_error: bool | None = None

Whether the tool use resulted in an error. Absent is equivalent to false.

meta class-attribute instance-attribute

meta: Meta | None = Field(alias='_meta', default=None)

Optional metadata. Clients SHOULD preserve this in subsequent sampling requests to enable caching optimizations.

ToolsCapability

Bases: MCPModel

Capability for tools operations.

Source code in src/mcp-types/mcp_types/_types.py

class ToolsCapability(MCPModel):
    """Capability for tools operations."""

    list_changed: bool | None = None
    """Whether this server supports notifications for changes to the tool list."""

list_changed class-attribute instance-attribute

list_changed: bool | None = None

Whether this server supports notifications for changes to the tool list.

ToolUseContent

Bases: MCPModel

An assistant's request to invoke a tool during sampling (2025-11-25+).

Appears in sampling/createMessage results and replayed assistant messages. The server should execute the tool and return a ToolResultContent in the next user message. Deprecated in 2026-07-28 (SEP-2577).

Source code in src/mcp-types/mcp_types/_types.py

class ToolUseContent(MCPModel):
    """An assistant's request to invoke a tool during sampling (2025-11-25+).

    Appears in `sampling/createMessage` results and replayed assistant messages.
    The server should execute the tool and return a `ToolResultContent` in the
    next user message. Deprecated in 2026-07-28 (SEP-2577).
    """

    type: Literal["tool_use"] = "tool_use"
    """Discriminator for tool use content."""

    name: str
    """The name of the tool to invoke. Must match a tool name from the request's tools array."""

    id: str
    """Unique identifier for this tool call, used to correlate with ToolResultContent."""

    input: dict[str, Any]
    """Arguments to pass to the tool. Must conform to the tool's inputSchema."""

    meta: Meta | None = Field(alias="_meta", default=None)
    """Optional metadata. Clients SHOULD preserve this in subsequent sampling
    requests to enable caching optimizations."""

type class-attribute instance-attribute

type: Literal['tool_use'] = 'tool_use'

Discriminator for tool use content.

name instance-attribute

name: str

The name of the tool to invoke. Must match a tool name from the request's tools array.

id instance-attribute

id: str

Unique identifier for this tool call, used to correlate with ToolResultContent.

input instance-attribute

input: dict[str, Any]

Arguments to pass to the tool. Must conform to the tool's inputSchema.

meta class-attribute instance-attribute

meta: Meta | None = Field(alias='_meta', default=None)

Optional metadata. Clients SHOULD preserve this in subsequent sampling requests to enable caching optimizations.

UnsubscribeRequest

Bases: Request[UnsubscribeRequestParams, Literal['resources/unsubscribe']]

Sent from the client to request cancellation of resources/updated notifications from the server. This should follow a previous resources/subscribe request.

Removed in protocol 2026-07-28; sent/received on sessions negotiating <= 2025-11-25. On 2026-07-28 use subscriptions/listen instead.

Source code in src/mcp-types/mcp_types/_types.py

class UnsubscribeRequest(Request[UnsubscribeRequestParams, Literal["resources/unsubscribe"]]):
    """Sent from the client to request cancellation of resources/updated notifications
    from the server. This should follow a previous resources/subscribe request.

    Removed in protocol 2026-07-28; sent/received on sessions negotiating <= 2025-11-25.
    On 2026-07-28 use `subscriptions/listen` instead.
    """

    method: Literal["resources/unsubscribe"] = "resources/unsubscribe"
    params: UnsubscribeRequestParams

UnsubscribeRequestParams

Bases: RequestParams

Parameters for a resources/unsubscribe request.

Removed in protocol 2026-07-28; sent/received on sessions negotiating <= 2025-11-25.

Source code in src/mcp-types/mcp_types/_types.py

class UnsubscribeRequestParams(RequestParams):
    """Parameters for a resources/unsubscribe request.

    Removed in protocol 2026-07-28; sent/received on sessions negotiating <= 2025-11-25.
    """

    uri: str
    """The URI of the resource to unsubscribe from."""

uri instance-attribute

uri: str

The URI of the resource to unsubscribe from.

UnsupportedProtocolVersionErrorData

Bases: MCPModel

Error data for the -32022 unsupported-protocol-version error (2026-07-28).

Source code in src/mcp-types/mcp_types/_types.py

class UnsupportedProtocolVersionErrorData(MCPModel):
    """Error data for the -32022 unsupported-protocol-version error (2026-07-28)."""

    supported: list[str]
    """Protocol versions the server supports; the client should pick one and retry."""

    requested: str

supported instance-attribute

supported: list[str]

Protocol versions the server supports; the client should pick one and retry.

UrlElicitationCapability

Bases: MCPModel

Capability for URL mode elicitation (2025-11-25+).

Source code in src/mcp-types/mcp_types/_types.py

class UrlElicitationCapability(MCPModel):
    """Capability for URL mode elicitation (2025-11-25+)."""

CONNECTION_CLOSED module-attribute

CONNECTION_CLOSED = -32000

SDK-only: the connection closed before a response arrived; never emitted on the wire.

HEADER_MISMATCH module-attribute

HEADER_MISMATCH = -32020

HTTP headers do not match the request body, or required headers are missing/malformed (protocol 2026-07-28).

INTERNAL_ERROR module-attribute

INTERNAL_ERROR = -32603

Standard JSON-RPC: an internal error occurred on the receiver.

The SDK uses the generic ErrorData envelope; the schema's per-code wrapper types are not constructed.

INVALID_PARAMS module-attribute

INVALID_PARAMS = -32602

Standard JSON-RPC: invalid method parameters.

INVALID_REQUEST module-attribute

INVALID_REQUEST = -32600

Standard JSON-RPC: the message is not a valid request object.

JSONRPC_VERSION module-attribute

JSONRPC_VERSION: Final[Literal['2.0']] = '2.0'

The JSON-RPC version string carried by every MCP message envelope.

METHOD_NOT_FOUND module-attribute

METHOD_NOT_FOUND = -32601

Standard JSON-RPC: the requested method does not exist or is not available.

MISSING_REQUIRED_CLIENT_CAPABILITY module-attribute

MISSING_REQUIRED_CLIENT_CAPABILITY = -32021

The server requires a client capability the request did not declare (protocol 2026-07-28).

PARSE_ERROR module-attribute

PARSE_ERROR = -32700

Standard JSON-RPC: invalid JSON was received.

REQUEST_TIMEOUT module-attribute

REQUEST_TIMEOUT = -32001

SDK-only: a request timed out waiting for its response.

UNSUPPORTED_PROTOCOL_VERSION module-attribute

UNSUPPORTED_PROTOCOL_VERSION = -32022

The request's protocol version is not supported by the server (protocol 2026-07-28).

URL_ELICITATION_REQUIRED module-attribute

URL_ELICITATION_REQUIRED = -32042

A URL-mode elicitation is required before the request can be processed (protocol 2025-11-25 only).

ErrorData

Bases: BaseModel

Error information for JSON-RPC error responses.

Source code in src/mcp-types/mcp_types/jsonrpc.py

class ErrorData(BaseModel):
    """Error information for JSON-RPC error responses."""

    code: int
    """The error type that occurred."""

    message: str
    """A short description of the error.

    The message SHOULD be limited to a concise single sentence.
    """

    data: Any = None
    """Additional information about the error.

    The value of this member is defined by the sender (e.g. detailed error information, nested errors, etc.).
    """

code instance-attribute

code: int

The error type that occurred.

message instance-attribute

message: str

A short description of the error.

The message SHOULD be limited to a concise single sentence.

data class-attribute instance-attribute

data: Any = None

Additional information about the error.

The value of this member is defined by the sender (e.g. detailed error information, nested errors, etc.).

JSONRPCError

Bases: BaseModel

A response to a request that indicates an error occurred.

Source code in src/mcp-types/mcp_types/jsonrpc.py

class JSONRPCError(BaseModel):
    """A response to a request that indicates an error occurred."""

    jsonrpc: Literal["2.0"]
    id: RequestId | None
    """The id of the request this error responds to.

    Required but nullable per JSON-RPC 2.0: `None` encodes `"id": null` (the id could not be determined).
    """

    error: ErrorData

id instance-attribute

id: RequestId | None

The id of the request this error responds to.

Required but nullable per JSON-RPC 2.0: None encodes "id": null (the id could not be determined).

JSONRPCMessage module-attribute

JSONRPCMessage = (
    JSONRPCRequest
    | JSONRPCNotification
    | JSONRPCResponse
    | JSONRPCError
)

Any JSON-RPC envelope that can be decoded off the wire or encoded to be sent.

JSONRPCNotification

Bases: BaseModel

A JSON-RPC notification which does not expect a response.

Source code in src/mcp-types/mcp_types/jsonrpc.py

class JSONRPCNotification(BaseModel):
    """A JSON-RPC notification which does not expect a response."""

    jsonrpc: Literal["2.0"]
    method: str
    params: dict[str, Any] | None = None

JSONRPCRequest

Bases: BaseModel

A JSON-RPC request that expects a response.

Source code in src/mcp-types/mcp_types/jsonrpc.py

class JSONRPCRequest(BaseModel):
    """A JSON-RPC request that expects a response."""

    jsonrpc: Literal["2.0"]
    id: RequestId
    method: str
    params: dict[str, Any] | None = None

JSONRPCResponse

Bases: BaseModel

A successful (non-error) response to a request.

Named JSONRPCResultResponse in the 2025-11-25+ schemas; the SDK keeps the original name.

Source code in src/mcp-types/mcp_types/jsonrpc.py

class JSONRPCResponse(BaseModel):
    """A successful (non-error) response to a request.

    Named `JSONRPCResultResponse` in the 2025-11-25+ schemas; the SDK keeps the original name.
    """

    jsonrpc: Literal["2.0"]
    id: RequestId
    result: dict[str, Any]

RequestId module-attribute

RequestId = Annotated[int, Field(strict=True)] | str

The ID of a JSON-RPC request.

LATEST_PROTOCOL_VERSION module-attribute

LATEST_PROTOCOL_VERSION: Final[str] = (
    KNOWN_PROTOCOL_VERSIONS[-1]
)

Newest protocol revision this SDK speaks (any era).