MCP Schema Version Support

[xbill9]

What happened?

The Rust rmcp MCP server library updated the default schema sent with the MCP request:

https://github.com/modelcontextprotocol/modelcontextprotocol/pull/655/files#top

previously this was:

http://json-schema.org/draft-07/schema#

now it sends:

https://json-schema.org/draft/2020-12/schema

which gives a transient error in Gemini CLI:

/mcp schema

Configured MCP servers:

🟢 HelloStdio - Ready (1 tool) Tools:

• greeting Hello World via Model Context Protocol Parameters: { "type": "object", "properties": { "message": { "description": "hello world", "type": "string" } }, "required": [ "message" ], "$schema": "https://json-schema.org/draft/2020-12/schema", "title": "GetMsgRequest" }

greetings from earth

╭───────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────╮ │ x greeting (HelloStdio MCP Server) {"message":"greetings from earth"} │ │ │ │ no schema with key or ref "https://json-schema.org/draft/2020-12/schema" │ ╰─────────────────────────────────────────────────────────────────────────────────

What did you expect to happen?

Gemini CLI would accept the updated schema and proceeed

Client information

Client Information

Run gemini to enter the interactive CLI, then run the /about command.

> /about

rmcp = { version = "0.11.0", features = ["auth", "server","macros", "transport-io"] }

Login information

No response

Anything else we need to know?

No response