fix(filesystem): use valid MCP content type for read_media_file#4044
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MukundaKatta wants to merge 1 commit intomodelcontextprotocol:mainfrom
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fix(filesystem): use valid MCP content type for read_media_file#4044MukundaKatta wants to merge 1 commit intomodelcontextprotocol:mainfrom
MukundaKatta wants to merge 1 commit intomodelcontextprotocol:mainfrom
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read_media_file returned content with type: "blob", which is not a
valid MCP content type per the 2025-11-25 spec (only text, image,
audio, resource_link, and resource are allowed). Strict clients
rejected the response at the transport layer with
"MCP error -32602: Invalid tools/call result".
Map the resolved MIME type to a valid content type:
- image/* -> { type: "image", data, mimeType }
- audio/* -> { type: "audio", data, mimeType }
- other -> { type: "resource", resource: { uri, mimeType, blob } }
Update the tool's outputSchema to match the new union shape and add
integration tests covering both the image and arbitrary-binary paths.
Closes modelcontextprotocol#4029.
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Closes #4029.
read_media_filereturned content withtype: "blob", which is not a valid MCP content type, so strict clients drop the response with "MCP error -32602: Invalid tools/call result". Mapped the file's MIME type to the correct MCP content (imagefor images,audiofor audio,resourcewith embedded blob for other binaries) and updatedoutputSchemato match.Tests added in
src/filesystem/__tests__/structured-content.test.ts.