API | BUILDER

Why API Builder?

AI agents using API Builder implement APIs correctly on the first try. The spec defines the contract, code generation produces trusted interfaces, and the compiler verifies everything matches.

✦ Compiler-Verified Correctness

  • Generated code is trusted — The agent doesn't write SDK code. It uses generated clients and server stubs. The generated code is high enough quality that teams stop writing client SDKs entirely.
  • The compiler becomes the test oracle — If your implementation compiles against the generated interfaces, it matches the spec. Compiler errors tell the agent exactly what's wrong — missing methods, wrong types, incorrect signatures.
  • Mock clients for testing — Generated mock clients share the same interface definition. Agents write meaningful tests without external dependencies and override only what's needed for each scenario.

⚡ Explicit Data Shapes

  • Every field and type defined upfront — Every resource, field, type, and relationship is declared in the spec. No guessing, no runtime discovery, no implicit conventions.
  • Spec as design input — Agents use the explicit data shapes to plan UX, database schemas, and data flows. The spec becomes input to both API implementation and frontend design.
  • First class union types — A type constrained to one of a known set. Agents know every valid state a value can be in — no open-ended polymorphism to handle.

⚙ Zero-Friction Workflow

  • Instant setup — api init creates an anonymous org and token. No signup, no email, no OAuth.
  • CLI-native — Everything is a CLI command agents can script: api validate, api (upload + generate).
  • Versioning built in — Every change to every API is recorded with safe and potentially breaking changes listed.

◆ Simple, Parseable Format

  • Flat JSON, no ambiguity — The api.json format is JSON — no YAML indentation issues, no $ref to resolve, no inheritance to trace.
  • Fully expanded output — The service specification is fully expanded and complete. An agent can read it and understand the entire API surface in one pass — no external references to follow.

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