Mobile Application API Documentation
Mobile team delivered a feature. Backend launched new endpoints. Then comes the question: "Where's the documentation?"—and it turns out there's none, or it's three sprints outdated. Familiar? This is where API documentation work begins.
What Exactly to Document
API documentation—not just URL list. For mobile app important to describe:
- All endpoints with methods, headers, parameters, request/response body examples
- Authorization schemes: Bearer token, OAuth 2.0, API Key—with header examples
- Error codes and meaning:
401 Unauthorizedvs403 Forbidden—difference matters on client - Pagination: cursor-based or offset, what meta fields returned
- Versioning:
/v1/,/v2/—what changed, what deprecated
How It's Done in Practice
For most projects we use combination: generate OpenAPI 3.x spec from code annotations (Laravel—L5-Swagger, NestJS—@ApiOperation decorators), then render via Stoplight Elements or Redoc as static site or built into dev portal.
If API exists but no docs—do reverse engineering: intercept traffic via Charles Proxy or mitmproxy, gather real requests from mobile app, recover structure. Slower but sometimes only option for legacy.
For React Native projects especially valuable to document types directly in TypeScript interfaces, then sync with OpenAPI schema via openapi-typescript. Gives you type-safe client without manual type writing.
Tools
| Tool | Scenario |
|---|---|
| Swagger UI / Redoc | Render OpenAPI spec |
| Stoplight Studio | Visual editor + mock server |
| Postman Collections | Testing + team sharing |
| Bruno | Postman alternative, file format in git |
| openapi-typescript | Generate TypeScript types from schema |
What Team Gets
Mobile developer stops asking backend "what returns if user not authorized". Tester sees all edge cases. QA automates contract testing by schema. PM understands what each call does.
Timeline depends on API size: small project (20-40 endpoints)—3-5 days, large service with complex schemas—up to 2-3 weeks with iterations.