Tools
The conformance suite's x-mcp-header number-type check finds a live bug in typescript-sdk main
modelcontextprotocol/conformance#444 (merged 2026-09-06T20:23Z) adds an `invalid_number_header` tool declaring `score: { type: 'number', 'x-mcp-header': 'Score' }`, the negative case SEP-2243 was actually about but that nothing exercised — the rule had only ever been tested via object/array/null values. Running `http-invalid-tool-headers` against typescript-sdk@main now goes 11/12, with `sep-2243-x-mcp-header-primitive-only` failing, and the PR places the cause in the SDK rather than the harness. It also corrects `sep-2243.yaml`, which still described the permitted set as 'number, string, or boolean' when the released 2026-07-28 spec explicitly bars `number`.
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