An API is a contract between a server and its clients. A predictable endpoint defines what resource it represents, which operations it accepts, what fields it returns, and how it reports invalid input or denied access.
Use serializers at the API boundary
Django REST Framework serializers convert model data into a response representation and validate incoming values. Keep allowed fields explicit. Read-only identifiers should not be accepted as user-controlled values, and ownership should come from the authenticated request rather than a submitted user ID.
Separate authentication from permissions
Authentication identifies the caller; permissions decide whether that caller may perform an action. Apply authorization to individual records as well as endpoints. A list endpoint should not reveal another user's records simply because the caller knows an identifier.
Make success and failure predictable
Return suitable HTTP status codes and structured validation messages so a browser client can show useful feedback. Use an API client during development to inspect requests, but keep automated tests for the expected contract.
- Test a valid request and the response fields it returns.
- Test blank, malformed, and out-of-range input.
- Test unauthenticated and unauthorized access.
- Test that a user cannot read or change another user's record.
These checks make API behavior easier to maintain as the frontend and data model evolve. Avoid putting secrets in browser code or trusting client-provided permissions.