docs: give the real reason outputSchema is not implemented - #125
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CLAUDE.md said the MCP spec asks for the payload to also be serialized into a text block, so a schema would send it twice. That is a SHOULD for old clients, not a MUST, and the spec's own example pairs an outputSchema with a text block that is not the serialized JSON. A lean TOON block is legal beside structuredContent. State the costs that are real instead: outputSchema is charged in tools/list on every turn, and a client may read structuredContent rather than our text block, which spends the shaping saving. Refs certinia#66
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Corrects one sentence in CLAUDE.md that gave a wrong reason for not implementing
outputSchema.What was wrong
CLAUDE.md said the MCP spec "asks for the payload to also be serialized into a text block, which would send it twice". The spec says:
SHOULD, notMUST, and it is there for old clients. The spec's own array example declares anoutputSchema, returnsstructuredContent, and puts prose in the text block instead of the serialized JSON. So a lean TOON block is legal besidestructuredContent, and the rule we recorded as blocking does not block anything.2026-07-28 does not change this. It relaxes the surrounding rules:
structuredContentmay be any JSON value, andoutputSchematakes the full JSON Schema 2020-12 vocabulary.What it says now
The two costs that are real and still unmeasured:
outputSchemarides intools/list, which every client loads on every turn, against a budget pinned at what 1.x charged.structuredContentrather than our text block, which spends the response-shaping saving.#66 is rewritten to measure both before deciding.
Refs #66