version

Protocol-version registry and comparison helpers.

Date-string protocol revisions happen to sort lexicographically, but versions are an enumerated set, not an ordered scalar: future identifiers are not guaranteed to be date-shaped, and unrecognized peer strings must compare conservatively instead of accidentally (e.g. "zzz" > "2025-11-25"). All ordering questions go through KNOWN_PROTOCOL_VERSIONS.

KNOWN_PROTOCOL_VERSIONS module-attribute

KNOWN_PROTOCOL_VERSIONS: Final[tuple[str, ...]] = (
    "2024-11-05",
    "2025-03-26",
    "2025-06-18",
    "2025-11-25",
    "2026-07-28",
)

Every released protocol revision, oldest to newest.

HANDSHAKE_PROTOCOL_VERSIONS module-attribute

HANDSHAKE_PROTOCOL_VERSIONS: Final[tuple[str, ...]] = (
    "2024-11-05",
    "2025-03-26",
    "2025-06-18",
    "2025-11-25",
)

Protocol revisions reachable via the initialize handshake.

MODERN_PROTOCOL_VERSIONS module-attribute

MODERN_PROTOCOL_VERSIONS: Final[tuple[str, ...]] = (
    "2026-07-28",
)

Protocol revisions that use the stateless per-request envelope.

SUPPORTED_PROTOCOL_VERSIONS module-attribute

SUPPORTED_PROTOCOL_VERSIONS: tuple[str, ...] = (
    *HANDSHAKE_PROTOCOL_VERSIONS,
    *MODERN_PROTOCOL_VERSIONS,
)

Deprecated: prefer HANDSHAKE_PROTOCOL_VERSIONS or MODERN_PROTOCOL_VERSIONS.

Kept as the union for v1.x compatibility.

LATEST_PROTOCOL_VERSION module-attribute

LATEST_PROTOCOL_VERSION: Final[str] = (
    KNOWN_PROTOCOL_VERSIONS[-1]
)

Newest protocol revision this SDK speaks (any era).

LATEST_HANDSHAKE_VERSION module-attribute

LATEST_HANDSHAKE_VERSION: Final[str] = (
    HANDSHAKE_PROTOCOL_VERSIONS[-1]
)

Newest revision reachable via the initialize handshake; the client's offer and server's counter-offer default.

LATEST_MODERN_VERSION module-attribute

LATEST_MODERN_VERSION: Final[str] = (
    MODERN_PROTOCOL_VERSIONS[-1]
)

Newest per-request-envelope revision; the server/discover probe default.

OLDEST_SUPPORTED_VERSION module-attribute

OLDEST_SUPPORTED_VERSION: Final[str] = (
    HANDSHAKE_PROTOCOL_VERSIONS[0]
)

Oldest revision this SDK still negotiates via the initialize handshake.

is_version_at_least

is_version_at_least(version: str, minimum: str) -> bool

Return True if version is a known revision at least as new as minimum.

Unknown version strings return False (treat unrecognized peers conservatively). minimum must be a member of KNOWN_PROTOCOL_VERSIONS; passing anything else is programmer error and raises ValueError.

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

def is_version_at_least(version: str, minimum: str) -> bool:
    """Return True if `version` is a known revision at least as new as `minimum`.

    Unknown `version` strings return False (treat unrecognized peers
    conservatively). `minimum` must be a member of KNOWN_PROTOCOL_VERSIONS;
    passing anything else is programmer error and raises ValueError.
    """
    if minimum not in KNOWN_PROTOCOL_VERSIONS:
        raise ValueError(f"minimum must be a known protocol version, got {minimum!r}")
    if version not in KNOWN_PROTOCOL_VERSIONS:
        return False
    return KNOWN_PROTOCOL_VERSIONS.index(version) >= KNOWN_PROTOCOL_VERSIONS.index(minimum)