Types-only install option

[KoolADE85]

Description

I'm integrating MCP server support into the Dash web framework. I want to leverage mcp.types to help ensure that responses and data structures are spec-compatible. Since Dash already manages its HTTP server, I don't want to use the SDK's server, client, or transports.

The problem: adding mcp to Dash's requirements pulls in ~15 transitive packages (starlette, httpx, etc) that are not necessary for leveraging the types.

I'd like to request a types-only install option that allows framework integrations to use only lightweight runtime types / protocol definitions.

References

It's fairly common to see lighter weight things like types/stubs published as a separate package that are then dependencies of the main package.

• langchain-core splits its types into a sibling langchain-protocol package and requires it as a dependency.
• pydantic requires its pydantic-core package.

In a similar vein, I'd like to require only mcp-types when I don't need all the server dependencies.

[Kludex]

I think we should follow the same structure as https://github.com/pydantic/httpx2/ (package wise), and publish mcp-types (it's under my handle, but happy to donate to mcp).