SEP-2243: ServerRejectsMissingMethodHeader contradicts TypeScript SDK behavior
Nobody has claimed this yet.
Assessment
- Difficulty
- 4/5
- Estimated time
- 3-5 days
- Newbie friendliness
- 42/100
- Issue type
- Bug
- Clarity
- Mostly clear
- Activity status
- Quiet
- Tech stack
- typescript
- Domain
- api, testing-qa
Research direction
Start with the http-header-validation scenario, especially ServerRejectsMissingMethodHeader, and trace connectToServer() through the TypeScript SDK's StreamableHTTPClientTransport. Compare the expected headers and results with the reported 108/1 and 64/32 outcomes; done means the conformance test and SDK behavior have a consistent, agreed expectation.
Written by the indexing model from the issue text.
Description
Description
The http-header-validation scenario's ServerRejectsMissingMethodHeader test sends a POST request without Mcp-Method header and expects the server to reject it with HTTP 400 + JSON-RPC error code -32001.
However, all other conformance scenarios (tools-list, tools-call-*, resources-*, prompts-*, etc.) use connectToServer() which creates a TypeScript SDK StreamableHTTPClientTransport — and this client does not send Mcp-Method headers.
This means:
- If a server implements SEP-2243 correctly (rejects missing
Mcp-Method), all SDK-backed scenarios fail (32+ failures) - If a server makes
Mcp-Methodoptional (to be compatible with the TypeScript SDK), theServerRejectsMissingMethodHeadertest fails
The conformance suite is self-contradictory: it tests a MUST requirement that the reference client implementation doesn't satisfy.
Expected behavior
Either:
- The TypeScript SDK should send
Mcp-Method(andMcp-Name) headers per SEP-2243, OR - The
ServerRejectsMissingMethodHeadertest should be downgraded from FAILURE to WARNING, since the reference client itself doesn't comply
Current C++ SDK result
With Mcp-Method optional (matching TypeScript SDK behavior): 108 passed, 1 failed
With Mcp-Method required (matching SEP-2243 spec): 64 passed, 32 failed
Related
- TypeScript SDK issue: https://github.com/modelcontextprotocol/typescript-sdk/issues/2176
- Dominant language
- TypeScript
- Stars
- 127
- Forks
- 101
- Avg merge
- 4d 7h
- Merged PRs (30d)
- 6
Contributor guide
First steps
- Read the whole issue, then the project's contributing guide.
- Comment on the issue to say you are picking it up — it saves two people doing the same work.
- Fork the repository and make your change on a branch.
- Open a pull request that references the issue number.
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