mcp is a library that lives inside other people's environments, so its requirements are chosen to constrain your resolver as little as possible while still describing what the SDK needs.

Every runtime dependency is a >= floor set to the oldest version that provides what the SDK uses, with no upper bound unless a dependency's next major is known to break the SDK. The one exception is mcp-types, the wire-types package released in lockstep with mcp: each mcp release requires exactly its own version of it, so it is the other half of the SDK rather than an independent constraint.

A floor is raised only when the SDK starts relying on functionality or a fix that first appeared in that version — not because the dependency published a security advisory. The >= bound already lets, and expects, you to run the newest release your other constraints allow, so a higher floor would only shrink the environments the SDK installs into; nor does the SDK add code to work around a dependency's vulnerability, since the fix belongs upstream and in your lockfile (background, python-sdk#1552). Floor raises may ship in a minor release under the versioning policy and are called out in the release notes. Adding a new runtime dependency, or moving one to its next major version, is decided in an issue before the pull request.

Dependabot opens monthly, grouped pull requests for the uv lockfile and for GitHub Actions. These refresh the versions the SDK is developed and tested against; the requirements published to PyPI move only under the rules above.