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Function calling schema builder

Define an LLM tool once with a one line field syntax and export it in the exact shapes OpenAI, Anthropic and Gemini expect, with per provider validation findings.

Name the tool and add parameters to see the provider exports.

The provider rules here are a dated snapshot of each API's documented limits, and Gemini is checked conservatively. A valid schema tells the API to accept the tool; it says nothing about whether a model picks the tool or fills it in sensibly. Treat every returned argument as untrusted input on your server.

Tool definition

Tool nameLetters, digits, underscores, dashes. 64 characters works everywhere.

DescriptionWhat it does, when to use it, when not to, and what it returns. Twelve words or more is a decent floor.

Parameters entry

Parameters, one per line? marks optional, enum(a|b) enumerates, [] makes a list, object takes indented children.

Example arguments

Example argumentsJSON array of argument objects. Include one call you expect to be rejected.

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Function calling schema builder

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