Convert OpenAPI endpoints into LLM tools
The OpenAPI → LLM Tool Schema Converter takes an OpenAPI 3.x specification and produces ready-to-use function-calling tool definitions for OpenAI or Anthropic. Pick exactly the endpoints you want the model to be able to call, and the tool merges their parameters into a single JSON Schema per operation.
How it works
The converter scans paths for every operation (GET, POST, PUT, PATCH, DELETE).
For each, it collects path and query parameters and, when present, the
application/json request-body schema, merging them into one properties object
with a combined required list. Parameter description fields are preserved so
the model understands each argument. The result is emitted in OpenAI’s
{ type: "function", function: {...} } shape or Anthropic’s { name, description, input_schema } shape, depending on your selection.
Tips and notes
Expose only the endpoints the model genuinely needs — fewer, well-described tools
beat a giant menu. Make sure your OpenAPI parameter description fields are
written for a model, not just a human reader, because that text is the model’s
only guidance on when and how to call the tool. If an operation lacks an
operationId, give it one in your spec so the generated tool name is stable.
Everything runs locally; nothing you paste leaves your browser.