API Documentation Prompt Builder

Ship accurate API docs without writing them by hand

Good API documentation is repetitive to write and easy to get subtly wrong. This builder takes the parts only you know — the endpoint, its schemas, and how it is authenticated — and produces a tightly scoped prompt that an LLM turns into complete, correctly formatted reference docs.

How it works

You provide six inputs: method, path, request schema, response schema, authentication scheme, and output format. The tool injects them into a prompt template engineered for accuracy. Key instructions tell the model to describe the endpoint in one sentence, enumerate every parameter with type and required flag, include a realistic curl example and matching response, and document the likely error codes. Critically, the prompt forbids inventing or dropping fields, so the docs match the schema you pasted.

Choosing OpenAPI 3.1 swaps the output instruction to emit a valid YAML path item — parameters, requestBody, responses, and security — ready to paste into a spec file. Markdown produces human-readable reference docs instead.

Tips for cleaner results

• Write schemas as field: type, notes lines — the model uses the notes to fill in descriptions and constraints.
• Include enum values and defaults in the notes (e.g. status: string (pending|shipped)); the model carries them into the parameter table.
• For OpenAPI output, run several endpoints and merge the path items under a single paths: key in your spec.
• If a 4xx case is business-specific, add it to the schema notes so the model documents it correctly rather than guessing.