How do you design APIs that other developers will love using?

Great API design is about developer experience—making your API intuitive and hard to misuse.

Consistency is paramount. Once you establish patterns (naming conventions, response shapes, error formats), stick to them everywhere. If GET /users returns { data: [...] }, every list endpoint should. Developers learn your patterns once and apply them everywhere.

Use HTTP semantics correctly. GET for reading (safe, cacheable), POST for creating, PUT/PATCH for updating, DELETE for removing. Return appropriate status codes: 200 for success, 201 for created, 400 for client errors, 404 for not found, 500 for server errors.

Design clear error responses. Include a code (machine-readable), message (human-readable), and relevant details. { "error": { "code": "VALIDATION_FAILED", "message": "Email is invalid", "field": "email" } }. Don't expose stack traces or internal details.

Resource naming uses plural nouns (/users, /posts), nests for relationships (/users/123/posts), and uses query parameters for filtering and pagination (/users?status=active&page=2).

Document everything. OpenAPI/Swagger specs enable auto-generated docs and client SDKs. Include examples for every endpoint. Document error cases, not just happy paths.

Version from the start (/v1/users). You will need to make breaking changes eventually. Versioning lets old clients continue working while new ones use updated endpoints.