API Documentation Writer
Write REST API docs in Markdown, OpenAPI 3.0 YAML, or Postman collection format.
This is an AI tool. The text you enter is sent to our AI service to generate your result. Our own server doesn't store it or use it for training; if it's down, a backup AI provider may handle it. How we handle your input
How to Use API Documentation Writer
- 1Pick the API style: REST, GraphQL or gRPC.
- 2Choose an output format — Markdown Docs, OpenAPI 3.0 YAML, or a Postman Collection.
- 3Describe the API: its endpoints, what they take, what they return, and how authentication works.
- 4Click 'Write API Documentation'.
- 5For OpenAPI output, validate the YAML in a spec validator or import it into Swagger UI before publishing — generated specs are frequently almost-valid.
Frequently Asked Questions
Is the OpenAPI output valid?
Usually close, and not reliably valid. Generated specs commonly have small schema errors — a misplaced required array, a `$ref` to something that does not exist. Run it through a validator or import it into Swagger UI, which will point at the line.
What does the Postman Collection output give me?
A collection structure with the requests, plus a list of environment variables to set and a short usage guide. You will need to fill in your real base URLs and auth values — it uses example.com placeholders deliberately rather than guessing your hosts.
Can it document an existing API from its code?
Not from code — describe the endpoints instead. If you want documentation generated from the implementation, a framework-native tool that reads your routes and types will be more accurate than any description you write from memory.
Does it document error responses?
Yes, including standard auth failures. Check them against what your API actually returns: the documented error shape is the contract clients code against, and getting it wrong causes more support load than an undocumented endpoint.
Which format should I choose?
OpenAPI if anything downstream consumes a spec — client generators, mock servers, API gateways. Markdown if humans are the only audience. Postman if the main use is letting someone try the API by hand.
About API Documentation Writer
The API Documentation Writer produces documentation for a REST, GraphQL or gRPC API in one of three formats: human-readable Markdown, an OpenAPI 3.0 spec, or a Postman collection with its environment variables and a usage guide.
The format choice should follow what consumes it. An OpenAPI spec is worth generating when something downstream reads it — client SDK generators, mock servers, gateway configuration — because then the spec is machine-checked by its consumers. Markdown is right when the only reader is a person.
Error responses are the section worth the most attention. The documented error shape is what client code branches on, and a documented error that does not match what your API actually returns generates more support tickets than an endpoint with no documentation at all. Check them against real responses.
Validate generated OpenAPI before publishing it — near-valid specs with a bad `$ref` or a misplaced `required` are the normal output, and a validator finds them in seconds. Base URLs come out as example.com placeholders rather than guesses, so replace them. Your input goes to our own AI server over HTTPS, is used once, and is never stored or used for training. If our server is down, a backup AI provider may handle the request under its own data policy.