Yes, AI can build a REST API, including routes, data access, validation, error handling, documentation, and tests. The result becomes dependable only when you give the agent an explicit contract and verify behavior at the boundaries, rather than asking it to invent the service from a vague feature description.
Start with the contract:
- Define resources, methods, request fields, response shapes, and status behavior.
- State authentication and authorization rules for every protected operation.
- Describe validation, pagination, idempotency, and expected failure cases.
- Identify the database schema and any external systems the API must call.
- Provide acceptance tests for normal, invalid, unauthorized, and repeated requests.
A plan-first agent can turn that contract into a route map, migration sequence, and test plan before writing code. Keep the first implementation narrow. Ask it to build one end-to-end resource, run tests, and show the diff. That reveals whether its conventions fit your codebase before it repeats them across the whole service.
Do not treat generated routes as production-ready because they return a successful response once. Review access control, secret handling, input limits, logging, and rollback behavior. AI is strong at mechanical implementation and test generation; the team still owns the service contract and threat model. A small, executable contract is the best starting prompt.
Related reading: How to write requirements for an AI coding agent and How to validate AI-generated code.
