mcp tools doesn't seem to follow protocol?

[maxandersen]

If I run:

mcp tools npx @jbangdev/jbang jdbc@mcp-java

I get:

error: RPC error -32601: The first message from the client must be "initialize": tools/list

should it not call initialize as defined in the protocol first?

note npx @jbangdev/jbang jdbc@mcp-java works fine with other MCP clients.

I also have similar issue when using mcp-proxy@quarkus.ai, but here it is:

mcp tools npx @jbangdev/jbang mcp-proxy@quarkus.ai

error: no response from command, stderr

again - this works with other mcp clients. hence my suspicion mcp is assuming something that is not following the protocol?

[f]

It actually follows the protocol but I'll try to fix if there's an issue on it.

[ayakut16]

@f I believe the protocol requires sending initialize request and initialized notification acknowledgement which is missing from mcptools.

• Documentation mentions this briefly here.
• Also here is the official python SDK sends this request upon initializing the client.

Most servers probably doesn't care about that but @jbangdev/jbang seem to enforces this request and fails otherwise, I believe this is the code that throws the error.

[mkouba]

Most servers probably doesn't care about that but @jbangdev/jbang seem to enforces this request and fails otherwise, I believe this is the code that throws the error.

Well, this is a spec requirement and it's described here (v2024-11-05) and here (v2025-03-26).

Note that the MCP server in question is built on top of quarkus-mcp-server which does not support 2025-03-26 yet.

[maxandersen]

it works! very much appreciated -thanks!