TRAPI 🦜REST API metadata & OpenAPI generation

Extract API metadata from TypeScript decorators and turn it into OpenAPI 2.0, 3.0, 3.1 or 3.2 specs — without adopting a new decorator library.

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What is TRAPI?

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Decorator-agnostic

Bring your own decorator library. Map any framework's decorators to TRAPI's semantic model — typescript-rest, @decorators/express, or your own.

See framework integration

Pure static analysis

Decorators stay as no-op markers. All work happens at build time through the TypeScript compiler API — no reflect-metadata, no runtime type information.

Read the philosophy

Faithful metadata

The metadata representation models TypeScript's type system directly — primitives, unions, intersections, tuples, utility types, generics. OpenAPI simplifications live only in the swagger layer.

Supported types

OpenAPI 2.0, 3.0, 3.1 & 3.2

One call to generateSwagger() emits a spec validated against the official OAI JSON Schemas. Save to disk as JSON or YAML.

Generate a spec

Composable pipeline

@trapi/metadata can be used on its own to power route generators, validators, or typed SDK tooling. The metadata is not tied to OpenAPI.

Key concepts

Reusable presets

Package a decorator mapping once and reuse it across projects. Presets can extend each other — no forced rewrites of existing controllers.

Write a custom preset