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Bad Request of "Missing Session Id" from a stateful MCP server

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Assessment

Difficulty
3/5
Estimated time
1-2 days
Newbie friendliness
48/100
Issue type
Bug
Clarity
Mostly clear
Activity status
Quiet
Tech stack
csharp
Domain
api

Research direction

Start by reproducing the ListServerTools call with the MCP Client SDK against a stateful MCP server, using the reported 400 response as the baseline. Read the linked stateful/stateless documentation and trace how the client handles the Mcp_Session_Id. Done means the request succeeds with the required session handling, or the expected client configuration is clearly documented.

Written by the indexing model from the issue text.

Description

needs repro

I used the MCP Client SDK and was trying to call a MCP server. With a test connection of calling the ListServerTools and got below response:

Response status code does not indicate success: 400 (Bad Request). Response body: {"jsonrpc":"2.0","id":"server-error","error":{"code":-32600,"message":"Bad Request: Missing session ID"}}

I have read the document here https://csharp.sdk.modelcontextprotocol.io/v1/concepts/stateless/stateless.html

In my understanding the client SDK should be able to handle the Mcp_Session_Id internally, or anything I have missed?

Dominant language
C#
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Merged PRs (30d)
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