About API Documentation from Code

Extract and generate API documentation from code endpoints with parameters and descriptions. Part of the DevTools Surf developer suite. Browse more tools in the API / Config collection.

Use Cases

• Generate initial API docs from existing Express or FastAPI endpoint handlers
• Extract parameter schemas from TypeScript route definitions
• Produce OpenAPI YAML for developer portal import
• Document internal APIs without maintaining a separate spec file

Tips

• Paste endpoint handler code with JSDoc/Python docstrings — the extractor uses comment annotations to populate parameter descriptions
• Include request/response examples as inline comments; they appear in the generated docs as code samples
• Use the 'OpenAPI export' button to get a machine-readable spec alongside the human-readable documentation

Fun Facts

• The OpenAPI Specification (formerly Swagger) was created by Wordnik in 2010 and open-sourced in 2015. It is now maintained by the Linux Foundation and has become the de facto standard for REST API documentation.
• Stripe's API documentation is frequently cited as the gold standard in developer experience — it was built from a custom internal toolchain, not a generic documentation generator.
• API documentation quality directly correlates with adoption: a 2022 Postman survey found that 71% of developers said poor documentation was the biggest barrier to consuming an API.

FAQ

Which languages and frameworks does the extractor support?

JavaScript/TypeScript (Express, Fastify, NestJS annotations), Python (FastAPI, Flask with docstrings), and Go (chi/gin with comments). The parser looks for route definitions and parameter types.

Is the output valid OpenAPI?

Yes — the generated spec targets OpenAPI 3.0 and can be imported into Swagger UI, Redoc, or Postman. Complex cases (nested discriminators, callbacks) may need manual adjustment.

How is this different from api-documentation-generator?

This tool extracts from code (bottom-up). The generator builds docs from manually provided details (top-down). Both produce similar output; this one is faster when you already have working code.