How Do I Document REST APIs?

Direct answer

Document a REST API in layers:

1. a quickstart for the first successful request;
2. conceptual guides for authentication, resources, and workflows;
3. a complete endpoint reference;
4. examples and SDK guidance;
5. errors, limits, pagination, webhooks, and troubleshooting;
6. version and migration documentation.

An OpenAPI document can power much of the reference, but developers still need explanations that connect endpoints to real tasks. See how to organize developer documentation for the surrounding information architecture.

Start with the first successful request

The quickstart should answer what users need before they begin, where credentials are created, which base URL to use, what the smallest valid request is, what response proves it worked, and what to do when it fails.

Keep the example complete. Include authentication headers, content type, required body fields, and a realistic response. A snippet that omits a required header creates a support ticket, not a successful integration.

Document the resource model

Explain the nouns before listing every route. For each resource, describe what it represents, who owns it, its lifecycle, relationships to other resources, immutable and mutable fields, and deletion or retention behavior.

This gives the API reference context. Without it, users can copy requests without understanding which operations are safe or how the objects relate.

Make endpoint reference complete

For every endpoint, document:

Method and path
Authentication
Path and query parameters
Headers
Request body schema
Successful responses
Error responses
Rate limits and pagination
Idempotency behavior
Version availability

Use consistent names and types. Explain defaults, nullable fields, enum values, maximum lengths, and whether the server ignores or rejects unknown fields.

Use OpenAPI as a contract

OpenAPI is useful for generating reference pages, clients, validation, and request examples. Treat the schema as a reviewed interface contract, not as a replacement for all documentation.

Keep human guidance beside generated reference pages. Link the endpoint to authentication, pagination, rate limits, error handling, and complete workflows.

Write errors as recovery paths

An error table should tell the reader what to check next:

Use the actual error shape returned by the API, including request IDs and safe troubleshooting details.

Explain asynchronous workflows

If an API queues work, document the lifecycle:

1. submit the job;
2. store the job ID;
3. poll or receive a webhook;
4. inspect completion or failure;
5. download the result;
6. handle expiration and cleanup.

State whether retries are safe, how long artifacts remain available, and which event fields are stable.

Add language-specific examples carefully

Show curl first when it is the clearest universal example, then add the languages your users actually use. Keep examples synchronized with the schema and test them where possible.

Avoid examples that hide important behavior behind a helper function. If a helper is required, link to its definition or explain what it does.

Keep versions and limits visible

Put version scope near the title and in code examples. Document request-size limits, rate limits, timeouts, pagination, retention, and plan restrictions. These details often matter more than another paragraph of marketing copy.

See how to version documentation for release-aware URL and migration patterns.

Test the docs

Before publishing, validate the OpenAPI document, run representative requests, test authentication, check examples, and verify that error responses match production behavior. Run link and anchor checks in CI.

When the API changes, review the quickstart, generated reference, examples, SDK notes, changelog, and migration guide together.

Conclusion

REST API documentation should help a developer reach a successful request, understand the resource model, implement the full workflow, and recover from failures. Use OpenAPI for a dependable contract, then add the task context and operational detail that generated reference pages cannot provide by themselves.