Unable to build client or server that would support the older 2024_11_05 rust-mcp-schema

[pnehrer]

I don't see a way to select the schema version at the rust-mcp-sdk crate. Would it be possible to expose the various version-selecting features from rust-mcp-schema in the sdk crate so that it'd be possible to build apps that support older protocol versions?

[hashemix]

Yea absolutely.

For servers, that won't be necessary. it's backward compatible. If you build an MCP server using rust-mcp-sdk, it will work with clients using either the 2025-03-26 or 2024-11-05 protocols. for instance rust-mcp-filesystem works with both protocol versions with no issue.

For clients, though, that absolutely makes sense 👍 . I've already started working on implementing protocol version switching using Cargo features and it will be shipped soon.

[hashemix]

Hey @pnehrer , I just published v0.4.2.

I plan to enhance rust-mcp-sdk support for multiple mcp protocole versions simultaneously, but for now v0.4.2 should unblock you , just use "2024_11_05" feature and disable the default-features:

rust-mcp-sdk = {version="0.4.2", default-features=false, features=["client","2024_11_05"]}