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…annotations headerSchemaProperty decoded every property's "type" as a string. JSON Schema allows an array there, and jsonschema.For emits ["null", T] for pointer fields. One such property made the remarshal of the whole inputSchema fail, so the tool was treated as having no x-mcp-header annotations at all: clients sent no Mcp-Param-* headers and servers skipped header validation for it. A boolean subschema had the same effect. Decode each property leniently. A non-string type is kept as its raw JSON text, so an annotated nullable property is still rejected by the primitive-type check. Fixes modelcontextprotocol#1406 Co-Authored-By: Claude Haiku 5.5 <noreply@anthropic.com> Signed-off-by: jay23606 <4602056+jay23606@users.noreply.github.com>
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Fixes #1406
What was broken
headerSchemaPropertydecoded each property'stypeas a plain string. JSON Schema also allowstypeto be an array, andjsonschema.Foremits"type": ["null", "string"]for every pointer field. A boolean subschema ("extra": true) is also valid JSON Schema.When any property in a tool's
inputSchemahad one of these shapes, decoding the whole schema failed and the SDK silently treated the tool as having nox-mcp-headerannotations at all, including on properties that were correctly annotated. The visible effects:Mcp-Param-*headers for the tool, so a server that validates them rejects the call withHeaderMismatch.validateParamHeaders, so a request whoseMcp-Param-*header contradicted the body was accepted.numberproperty) were not reported byAddToolor the client'stools/listfilter.What changed
headerSchemaPropertynow has its ownUnmarshalJSON, so each property decodes independently:typeis kept as its raw JSON text. It therefore still fails the existing primitive-type check, so an annotated nullable property (["null", "string"]) is still rejected, as before.The change is confined to
mcp/streamable_headers.go. No exported API changes.How it was tested
TestExtractToolParamHeaders(an array-typed sibling and a boolean subschema must not hide an annotated property) and toTestValidateToolParamHeaders(an invalid annotation next to an array-typed or boolean sibling must be reported, and a nullable annotated property must be rejected). All five new cases fail on the unmodified code and pass with this change.go test ./mcp/...passes,go vet ./mcp/is clean, and the touched files are gofmt-clean.This patch was prepared with AI assistance (Claude Code). The failure mode and the test cases were checked by hand against the code paths listed above.
🤖 Generated with Claude Code