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",
)

Every released protocol revision, oldest to newest.

SUPPORTED_PROTOCOL_VERSIONS module-attribute

SUPPORTED_PROTOCOL_VERSIONS: list[str] = [
    "2024-11-05",
    "2025-03-26",
    "2025-06-18",
    LATEST_PROTOCOL_VERSION,
]

Protocol revisions this SDK can negotiate.

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/shared/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)