OpenAPI

Because the request pipeline is data you can read, green-tea can project it — the same way it renders Mermaid/DOT, it emits OpenAPI.

app.openapi()

const app = createApp({ modules: [ApiModule] });
const spec = app.openapi({ title: 'My API', version: '1.0.0' });
// → OpenAPI 3.1 document

It reads the routes and handler signatures and produces, for each route:

• the path, templated — /users/:id → /users/{id}, constrained :id(\d+) → {id}, catch-all :path* → {path};
• the explicitly declared method, including @Head and @Options;
• parameters — path params from the pattern, plus query/header params from the handler’s @query / @headers / @header decorators;
• a request body entry for routes that read @body();
• the systematic responses — 200, a 422 when any argument is schema-validated, and 500.

WebSocket routes are omitted (they aren’t request/response).

A constrained path parameter remains a string parameter and carries its route expression as schema.pattern. Only declared operations appear: implicit HEAD and automatic OPTIONS fallbacks are runtime conveniences and are not invented in the OpenAPI document.

Serve it — devOpenapi

Opt in to a GET /__openapi__ endpoint that returns the document as JSON — point Swagger UI, Redoc, or a codegen client at it:

const app = createApp({ modules: [ApiModule], devOpenapi: true });
// GET /__openapi__  →  application/json

What’s structural (and what isn’t yet)

This is a structural spec: paths, methods, parameters, which routes take a body, and the standard error responses. What it does not include yet:

• Request/response body schemas. Standard Schema (zod/valibot/arktype) validates input but does not expose a JSON Schema representation, so body shapes are documented generically. Parameter types default to string.

Full schemas — declared and enforced on the way out via a @Produce(schema) decorator that also validates responses — are on the roadmap for the stable release. For beta, the structural document already drives Swagger UI, client codegen, and API diffing.