FastAPI
The Python framework that turns annotated functions into a self-documenting HTTP API. You declare your parameter types, FastAPI derives input validation, output serialization and interactive docs served at `/docs`. It runs asynchronously by default, which matters when every request is waiting on a model call. It has become the default way to put an API layer in front of an agent or a model without writing plumbing.
Strengths
- Input validation and docs come from the type annotations, with no extra code
- Async by default: a request waiting on a model call does not tie up the server
- Interactive docs served automatically, handy to let someone test without reading your code
Limitations
- Python ecosystem only: no help if your product lives in TypeScript
- Nothing provided for rate limiting or authentication: those are pieces you add yourself
Best for
- Exposing a Python agent or pipeline behind a URL the rest of the product can call
- Prototyping an API with testable docs without hand-writing a schema