Simplify error response when accessing MCP without session ID

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#577 3 comments 0 reactions 0 assignees View on GitHub

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Assessment

Difficulty
2/5
Estimated time
1-3 hours
Newbie friendliness
68/100
Issue type
Bug
Clarity
Clearly specified
Activity status
Quiet
Tech stack
java
Domain
api, backend

Research direction

Start at HttpServletStreamableServerTransportProvider.java around line 264 and inspect the GET handling for requests without an mcp-session-id header. Reproduce the request described in the issue, then verify the response gives a simple request or session-ID message without exposing the exception stack trace.

Written by the indexing model from the issue text.

Description

enhancement waiting for triage

Description:
Currently, when accessing the MCP Streamable HTTP server at https://host:port/mcp without providing a session ID, the server responds with the full exception stack trace and detailed error information.

Issue:
Returning the complete stack trace in the response is not user-friendly and may expose internal details unnecessarily.

https://github.com/modelcontextprotocol/java-sdk/blob/7f16cd0b9dc72f5adc3358a903bebb0f909dda3e/mcp-core/src/main/java/io/modelcontextprotocol/server/transport/HttpServletStreamableServerTransportProvider.java#L264C4-L264C100

Suggestion:
Instead of returning the full error, return a simple, clear message indicating there is an issue with the request headers or the session ID

stack trace

{
  "cause": null,
  "stackTrace": [
    {
      "moduleName": null,
      "moduleVersion": null,
      "classLoaderName": null,
      "methodName": "doGet",
      "fileName": "HttpServletStreamableServerTransportProvider.java",
      "lineNumber": 268,
      "className": "com.ibm.modelcontextprotocol.server.transport.HttpServletStreamableServerTransportProvider",
      "nativeMethod": false
    },
    {
      "moduleName": null,
      "moduleVersion": null,
      "classLoaderName": null,
      "methodName": "service",
      "fileName": "HttpServlet.java",
      "lineNumber": 527,
      "className": "jakarta.servlet.http.HttpServlet",
      "nativeMethod": false
    },
    {
      "moduleName": null,
      "moduleVersion": null,
      "classLoaderName": null,
      "methodName": "service",
      "fileName": "HttpServlet.java",
      "lineNumber": 614,
      "className": "jakarta.servlet.http.HttpServlet",
      "nativeMethod": false
    }
  ],
  "jsonRpcError": null,
  "message": "text/event-stream required in Accept header; Session ID required in mcp-session-id header",
  "localizedMessage": "text/event-stream required in Accept header; Session ID required in mcp-session-id header",
  "suppressed": []
}
Dominant language
Java
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Avg merge
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Merged PRs (30d)
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