Build Workspace App

pip install openbb --no-deps

Architecture Overview

OpenBB is built on FastAPI and Pydantic. The application has two independent interfaces that share core logic and models:

• Python Interface — wraps installed routers into an obb Python package with auto-generated docstrings and function signatures. Requires a build step (openbb-build) to generate static assets.
• REST API — a FastAPI instance with all installed routers available via HTTP. Import it with from openbb_core.api.rest_api import app or launch with uvicorn openbb_core.api.rest_api:app.

The application is the product of all installed extensions. With just openbb-core there are no routers or endpoints — users compose their own combinations.

Key Classes

Router Extensions (API Endpoints)

Router extensions are the user-facing endpoints that power the REST API, MCP, and Python Interface.

Creating a Router

from openbb_core.app.model.obbject import OBBject
from openbb_core.app.router import Router

router = Router(prefix="", description="My custom extension.")

The top-level API path prefix is determined by the entry point name in pyproject.toml, not the prefix argument. Only use prefix for sub-routers.

[tool.poetry.plugins."openbb_core_extension"]
my_app = "my_package.routers.my_router:router"

Commands appear at /my_app/... in the API and obb.my_app. in Python.

Provider Interface Endpoints

Connect a router command to one or more provider fetchers via the model name:

from openbb_core.app.model.command_context import CommandContext
from openbb_core.app.model.obbject import OBBject
from openbb_core.app.provider_interface import ExtraParams, ProviderChoices, StandardParams
from openbb_core.app.query import Query
from pydantic import BaseModel

@router.command(model="MyModel")
async def my_command(
    cc: CommandContext,
    provider_choices: ProviderChoices,
    standard_params: StandardParams,
    extra_params: ExtraParams,
) -> OBBject[BaseModel]:
    """Description of this command."""
    return await OBBject.from_query(Query(**locals()))

The four parameters and the OBBject.from_query(Query(**locals())) return are mandatory and must be used exactly as shown.

Basic GET Endpoint

@router.command(methods=["GET"])
async def hello() -> OBBject[str]:
    """OpenBB Hello World."""
    return OBBject(results="Hello from the extension!")

Basic POST Endpoint

from openbb_core.provider.abstract.data import Data

@router.command(methods=["POST"])
async def process(data: Data, some_param: str) -> OBBject:
    """Process submitted data."""
    return OBBject(results=data.model_dump())

Decorator Parameters

@router.command accepts:

• model — metamodel name linking to Provider fetchers
• methods — list of HTTP methods, typically ["GET"] or ["POST"]
• examples — list of APIEx or PythonEx for docs
• deprecated — deprecation notice
• exclude_from_api — Python Interface only
• no_validate — skip response validation, treat output as Any
• openapi_extra — dictionary for inline widget_config or mcp_config

Using FastAPI APIRouter Directly

Access the underlying FastAPI router via router._api_router:

@router._api_router.get("/also_empty")
async def also_empty(param: str) -> str:
    """Also empty."""
    return "Hello world!"

From FastAPI — Converting Existing Apps

Any existing FastAPI application can become an OpenBB extension without changing code. Define the entry point in pyproject.toml pointed at the FastAPI or APIRouter instance:

[tool.poetry.plugins."openbb_core_extension"]
my_app = "my_package.app:app"

Install the package and build static assets:

pip install -e .
openbb-build

Known limitations:

• Authorization hooks are not injected into the Python Interface
• Request-bound dependencies or those returning None are not injected
• WebSockets are not supported in the Python Interface
• Multi-method routes (GET + POST on same path) may not generate correctly

Serving with openbb-api (Workspace Backends)

The openbb-api CLI converts a FastAPI instance into an OpenBB Workspace backend with auto-generated widget definitions.

Basic Usage

# Start with default OpenBB extensions
openbb-api

# Start with a custom FastAPI file
openbb-api --app ./my_app.py --host 0.0.0.0 --port 8005

# Factory function pattern
openbb-api --app my_app.py:create_app --factory

# Custom FastAPI instance name
openbb-api --app my_app.py --name my_app

Defaults are --host 127.0.0.1 --port 6900, falling back to the next available port if already in use.

Key Arguments

All remaining arguments are passed to uvicorn.run.

Inline Widget Definitions

Widget properties can be defined inline in your code via openapi_extra:

@app.get(
    "/some_endpoint",
    openapi_extra={
        "widget_config": {
            "name": "Custom Widget Name",
            "description": "Override docstring description",
        }
    },
)
async def some_endpoint():
    """Description from docstring."""
    pass

Exclude an Endpoint from Widgets

@app.get(
    "/internal_endpoint",
    openapi_extra={"widget_config": {"exclude": True}},
)
async def internal_endpoint():
    return [{"label": "Choice 1", "value": "choice1"}]

Dropdown Parameters

Dropdowns are auto-generated from Literal types:

from typing import Literal

@app.get("/with_dropdown")
async def with_dropdown(
    choices: Literal["Choice 1", "Choice 2", "Choice 3"] = "Choice 3"
):
    pass

Column Definitions for Tables

Use Pydantic response models to auto-generate table column definitions:

import datetime
from pydantic import BaseModel, Field

class MyData(BaseModel):
    date: datetime.date = Field(description="The date.")
    value: float = Field(description="The value.")

@app.get("/my_data")
async def my_data() -> list[MyData]:
    """Widget with typed columns."""
    return [MyData(date=datetime.date.today(), value=42.0)]

Widget Types by Return Type

Response Models for Special Widgets

from openbb_platform_api.response_models import MetricResponseModel, PdfResponseModel

@app.get("/metric", response_model=MetricResponseModel)
async def metric():
    """A metric widget."""
    return dict(label="Revenue", value=12345, delta=5.67)

@app.get("/pdf", response_model=PdfResponseModel)
async def open_pdf(file_path: str):
    """Open a PDF document."""
    with open(file_path, "rb") as f:
        return dict(content=f.read())

Plotly Chart Widget

@app.get(
    "/chart",
    openapi_extra={"widget_config": {"type": "chart"}},
)
async def chart() -> dict:
    """A chart widget."""
    from plotly.graph_objs import Bar, Layout, Figure

    fig = Figure(
        data=[Bar(x=["A", "B", "C"], y=[1, 2, 3])],
        layout=Layout(title="My Chart", template="plotly_dark"),
    )
    return fig.to_plotly_json()

JSON Schema Extra for Parameters

Annotate parameters with additional widget configuration:

from typing import Annotated
from fastapi import Query

my_param: Annotated[
    str,
    Query(
        title="My Title",
        description="Detailed hover text",
        json_schema_extra={
            "x-widget_config": {
                "optionsEndpoint": "/my_choices_endpoint"
            }
        },
    ),
]

Form Input Widget

Create an input form tied to a table:

• GET endpoint defines widget_config.form_endpoint pointing to the POST route
• POST route accepts a single Pydantic model argument

OBBject Extensions (Result Post-Processing)

Extend the OBBject response with custom methods, accessible in the Python Interface.

Class Accessor (Namespaced Methods)

from openbb_core.app.model.extension import Extension

ext = Extension(name="my_tools", description="Custom result tools.")

@ext.obbject_accessor
class MyTools:
    def __init__(self, obbject):
        self._obbject = obbject

    def summary(self):
        """Return a summary."""
        return self._obbject.to_dataframe().describe()

Register in pyproject.toml:

[tool.poetry.plugins."openbb_obbject_extension"]
my_tools = "my_package.obbject.my_ext:ext"

Callable Accessor (Property-Like)

ext = Extension(name="to_csv", description="Convert results to CSV.")

@ext.obbject_accessor
def to_csv(obbject):
    """Convert to CSV string."""
    return obbject.to_dataframe().to_csv()

OBBject Output Conversion Methods

Every OBBject has built-in conversion methods:

• to_df() / to_dataframe() — Pandas DataFrame
• to_dict(orientation=...) — Python dict
• to_numpy() — NumPy array
• to_polars() — Polars DataFrame (requires polars installed)
• model_dump() — Complete object as dict
• model_dump_json() — Serialized JSON string

OBBject Plugins (Pre-Return Interceptors)

Plugins execute before the response is returned, compatible with both REST API and Python Interface. They can conditionally alter the output of any command.

WARNING: Plugins are considered potentially dangerous. The environment must be explicitly configured to allow them.

In system_settings.json:

{
    "allow_on_command_output": true,
    "allow_mutable_extensions": true
}

Plugin Configuration

from openbb_core.app.model.extension import Extension

plugin = Extension(
    name="my_plugin",
    description="Intercept output before return.",
    on_command_output=True,
    command_output_paths=["/my_router/my_command"],
    immutable=False,
    results_only=False,
)

Key parameters:

• on_command_output=True — required for plugins
• command_output_paths — list of endpoint paths to intercept (None = all)
• immutable=False — set to allow modifying the response object
• results_only=True — receive only the results portion instead of full OBBject

Plugin Code

@plugin.obbject_accessor
def my_plugin_func(obbject):
    """Modify or inspect the response before it returns."""
    # Modify obbject directly; do NOT return anything
    pass

Charting Extensions (Views)

Add custom chart views to any router endpoint, activated when the user sets chart=True.

Structure

from typing import TYPE_CHECKING, Any

if TYPE_CHECKING:
    from openbb_charting.core.openbb_figure import OpenBBFigure

class MyViews:
    """Chart views for the router."""

    @staticmethod
    def my_router_my_command(**kwargs) -> tuple["OpenBBFigure", dict[str, Any]]:
        """Chart for my_command."""
        from openbb_charting.core.openbb_figure import OpenBBFigure

        data = kwargs["obbject_item"]
        fig = OpenBBFigure()
        # Build chart with fig.add_*() methods
        content = fig.show(external=True).to_plotly_json()
        return fig, content

Method naming convention: <router_name>_<command_name> matching the route path in lower_snake_case.

Register in pyproject.toml:

[tool.poetry.plugins."openbb_charting_extension"]
my_router = "my_package.routers.my_views:MyViews"

Kwargs Available in Views

HTTP Requests in Fetchers

Use the built-in utilities instead of creating new clients from scratch.

Query String Helper

from openbb_core.provider.utils.helpers import get_querystring

query_string = get_querystring(query.model_dump(), ["exclude_this_param"])

Synchronous Requests

from openbb_core.provider.utils import make_request

response = make_request(url, headers=headers, params=params)

Requests Session

from openbb_core.provider.utils.helpers import get_requests_session

session = get_requests_session()

Asynchronous Requests (AIOHTTP)

from openbb_core.provider.utils.helpers import amake_request

response_json = await amake_request(url)

Multi-URL Async Requests

from openbb_core.provider.utils.helpers import amake_requests

results = await amake_requests([url1, url2, url3])

Custom Response Callback

from io import StringIO
from pandas import DataFrame

results = []

async def response_callback(response, _):
    text = await response.text()
    data = DataFrame(StringIO(text), skiprows=2)
    results.append(data.to_dict("records"))

await amake_requests(url, response_callback=response_callback)

Async Session

from openbb_core.provider.utils.helpers import get_async_requests_session

async with await get_async_requests_session() as session:
    async with await session.get(url) as response:
        data = await response.json()

Async Fetchers

Use aextract_data instead of extract_data for async fetchers:

@staticmethod
async def aextract_data(
    query: MyQueryParams,
    credentials: dict[str, str] | None,
    **kwargs: Any,
) -> list[dict]:
    """Async data extraction."""
    ...

Testing

Built-In Fetcher Test

Every Fetcher has a .test() method for quick validation:

from my_package.providers.my_provider.models.my_model import MyFetcher

fetcher = MyFetcher()
fetcher.test({"symbol": "AAPL"}, {})  # Returns None on success

Unit Tests with Cassettes

Install dev tools and use pytest_recorder for HTTP cassette recording:

pip install openbb-devtools
pytest test_my_fetcher.py --record http

Subsequent test runs replay the recorded HTTP interactions.

Running Tests

# Unit tests only
pytest tests/ -m "not integration"

# Integration tests only
pytest tests/ -m integration

# All tests
pytest tests/

Integration Testing

For API integration tests, start a local server first:

uvicorn openbb_core.api.rest_api:app --host 0.0.0.0 --port 8000 --reload

Install and Build

Development Install

From the project root:

pip install -e ".[dev]"

Build Python Interface

After installing or removing extensions, regenerate static assets:

openbb-build

Verify in Python

from openbb import obb
# Your commands appear under obb.<router_name>.<command_name>()

Serve as Workspace Backend

openbb-api --app ./my_app.py --editable --host 0.0.0.0 --port 6900

Workflow Summary

When a user asks "Build me a Workspace application that does X":

1. Scaffold the project with openbb-cookiecutter (see develop_extension skill).
2. Remove example files and clean up boilerplate.
3. Implement fetchers for each data source in providers/<name>/models/.
4. Register fetchers in providers/<name>/__init__.py via fetcher_dict.
5. Implement router commands in routers/<name>.py.
6. Add widget config via openapi_extra for Workspace-specific behavior.
7. Update pyproject.toml entry points and dependencies.
8. Install with pip install -e ".[dev]".
9. Build static assets with openbb-build.
10. Serve with openbb-api and verify widgets in OpenBB Workspace.
11. Test with pytest and fetcher .test() methods.