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Version: v5

From FastAPI

An existing FastAPI application becomes an OpenBB extension without code changes. Point an openbb_core_extension entry point at a configured fastapi.FastAPI or fastapi.APIRouter instance, install the package, and each route is served by the OpenBB REST API and generated as a method on obb. Quick start (Developer) walks through a minimal example; this page covers the details and the limits.

Register the entry point​

Add openbb-core to the project's dependencies and declare the entry point:

[project]
dependencies = ["openbb-core>=2.0.0"]

[project.entry-points."openbb_core_extension"]
my_app = "my_package.app:app"

The object after the colon must exist when the module is imported. Factory functions are not called, so an entry point that resolves to a function is skipped. A FastAPI app contributes its router; an APIRouter is used directly. The entry-point name, my_app here, becomes the namespace: a route at /prices becomes obb.my_app.prices() and /api/v1/my_app/prices. Any build backend that writes standard entry-point metadata works.

Install, build, and import​

pip install -e .
openbb-build
from openbb import obb

obb.my_app

The REST API picks up the routes on its next start without a build. The build is only for the Python Interface. It generates each method's signature from the route's parameters and its docstring from the route's description and models, and it adds the routes to obb.reference. Pydantic models with field descriptions produce more useful docstrings than bare types.

How routes behave in the Python Interface​

The Python Interface calls the route function directly, without an HTTP request, so anything that depends on the request needs attention.

Dependencies declared with Depends() are resolved in-process when possible. A dependency whose own parameters are headers, cookies, query parameters, or plain values has those parameters added to the generated method and called with them, so an x-api-key header dependency becomes an x_api_key argument. A dependency that needs a Request, Response, or WebSocket object, or that nests another Depends(), cannot be resolved without a request. Avoid reading the request object inside handlers you want to call from Python.

Authentication applied by the REST server does not run in the Python Interface; the caller is already inside the process.

WebSocket routes are served by the REST API but are not generated in the Python Interface. A handler that returns a Starlette StreamingResponse is returned in Python as an OBBStream over the response body, and over REST the response is forwarded unchanged.

The Python Interface identifies commands by path, so two routes with the same path and different HTTP methods produce one method. Give each operation its own path, or use a path parameter. Routes declared with include_in_schema=False are left out of the Python Interface.

Flask applications​

With the flask extra installed (pip install "openbb-core[flask]"), an openbb_core_extension entry point can also point to a Flask app. The REST API mounts it at /api/v1/<entry-point name> and merges its routes into the OpenAPI schema. Flask apps are not added to the Python Interface.

Troubleshooting​

If openbb-build fails, set OPENBB_DEBUG_MODE=true and run it again for the full traceback. Errors usually point to an import that fails outside the server, or to a type annotation that cannot be written into generated code. Building from Python with openbb.build(lint=False) skips the ruff pass, which separates generation errors from lint errors. If the problem is hard to isolate in a large app, register one APIRouter at a time.

The generated files are in the environment's site-packages/openbb/package/ directory, one module per path, and are safe to read when a generated signature looks wrong. Rebuilding replaces them. If a problem persists with the latest openbb-core, open an issue on GitHub with the error, the original route, and the generated code.

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