FastOpenAPI is a library for generating and integrating OpenAPI schemas using Pydantic and various frameworks.
This project was inspired by FastAPI and aims to provide a similar developer-friendly experience.
Links
- Documentation: Docs
- Repository: GitHub
- PyPi: FastOpenAPI
Why FastOpenAPI?
It was built out of frustration with fragmented tooling and inconsistent documentation standards across frameworks. FastOpenAPI aims to bring the developer experience of FastAPI — automatic docs, validation, and schema generation — to any Python web stack, with minimal dependencies and maximum control.
FastOpenAPI is especially useful when:
- You want OpenAPI documentation without being locked into a single framework
- You need consistent API docs across a multi-service architecture
- You prefer Pydantic v2 models and want tight integration.
Most OpenAPI tools are tied to a specific framework, like FastAPI or Flask. FastOpenAPI breaks that limitation by offering a shared, flexible engine that works across:
- AioHttp
- Flask
- Falcon
- Quart
- Starlette
- Sanic
- Tornado
Instead of forcing migration to a specific stack, FastOpenAPI uses lightweight "proxy routing" to register endpoints in a FastAPI-like style — while integrating directly with your existing framework.
The library supports router composition (like FastAPI's APIRouter), automatic Swagger and ReDoc generation, and provides strong Pydantic v2-based typing and validation.