Temporarily adopting this point of view (of the *external developer*) can help you feel like it's more obvious where to put the parameters, the Pydantic model for the body, for the response, etc. for that *external API*.

### Create a callback `APIRouter`

First create a new `APIRouter` that will contain one or more callbacks.

```Python hl_lines="3  25"
{!../../../docs_src/openapi_callbacks/tutorial001.py!}
```

# FastAPI CLI

**FastAPI CLI** is a command line program `fastapi` that you can use to serve your FastAPI app, manage your FastAPI project, and more.

When you install FastAPI (e.g. with `pip install fastapi`), it includes a package called `fastapi-cli`, this package provides the `fastapi` command in the terminal.

To run your FastAPI app for development, you can use the `fastapi dev` command:

<div class="termy">

```console

You will get completion in code you might even consider impossible before. As for example, the `price` key inside a JSON body (that could have been nested) that comes from a request.

No more typing the wrong key names, coming back and forth between docs, or scrolling up and down to find if you finally used `username` or `user_name`.

### Short

* Data conversion
* Data validation
* Automatic documentation

## Special types and validation

Apart from normal singular types like `str`, `int`, `float`, etc. you can use more complex singular types that inherit from `str`.

    But when the form includes files, it is encoded as `multipart/form-data`. If you use `File`, **FastAPI** will know it has to get the files from the correct part of the body.

## Opiniões

"*[...] Estou usando **FastAPI** muito esses dias. [...] Estou na verdade planejando utilizar ele em todos os times de **serviços _Machine Learning_ na Microsoft**. Alguns deles estão sendo integrados no _core_ do produto **Windows** e alguns produtos **Office**.*"

    description: Optional[str] = None
    url: AnyUrl


class Schema(BaseModelWithConfig):
    # Ref: JSON Schema 2020-12: https://json-schema.org/draft/2020-12/json-schema-core.html#name-the-json-schema-core-vocabu
    # Core Vocabulary
    schema_: Optional[str] = Field(default=None, alias="$schema")
    vocabulary: Optional[str] = Field(default=None, alias="$vocabulary")

```

...and see how your editor will auto-complete the attributes and know their types:

![editor support](https://fastapi.tiangolo.com/img/vscode-completion.png)

For a more complete example including more features, see the <a href="https://fastapi.tiangolo.com/tutorial/">Tutorial - User Guide</a>.

**Spoiler alert**: the tutorial - user guide includes:

                """
            ),
            deprecated(
                """
                "openapi_prefix" has been deprecated in favor of "root_path", which
                follows more closely the ASGI standard, is simpler, and more
                automatic.
                """
            ),
        ] = "",
        root_path: Annotated[
            str,
            Doc(
                """

And the dependency function `get_current_active_user` can also declare sub-dependencies, not only with `Depends` but also with `Security`. Declaring its own sub-dependency function (`get_current_user`), and more scope requirements.

In this case, it requires the scope `me` (it could require more than one scope).

!!! note