You will learn more about adding extra information later in the docs, when learning to declare examples.

!!! warning
    Extra keys passed to `Field` will also be present in the resulting OpenAPI schema for your application.

app = FastAPI()

app.add_middleware(UnicornMiddleware, some_config="rainbow")
```

`app.add_middleware()` receives a middleware class as the first argument and any additional arguments to be passed to the middleware.

## Integrated middlewares

**FastAPI** includes several middlewares for common use cases, we'll see next how to use them.

!!! note "Technical Details"

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test_main.py <span style="color: green; white-space: pre;">......                            [100%]</span>

<span style="color: green;">================= 1 passed in 0.03s =================</span>
```

You can declare path "parameters" or "variables" with the same syntax used by Python format strings:

```Python hl_lines="6-7"
{!../../../docs_src/path_params/tutorial001.py!}
```

The value of the path parameter `item_id` will be passed to your function as the argument `item_id`.

So, if you run this example and go to <a href="http://127.0.0.1:8000/items/foo" class="external-link" target="_blank">http://127.0.0.1:8000/items/foo</a>, you will see a response of:

So, if the `dict` contains:

```Python
{
    "username": "johndoe",
    "hashed_password": "some_hash",
}
```

It will be passed to `UserInDB` as:

```Python
UserInDB(username="johndoe", hashed_password="some_hash")
```

## Create your **FastAPI** code

### Create the `FastAPI` app

```Python hl_lines="46"

    ```Python hl_lines="17"
    {!> ../../../docs_src/dependencies/tutorial006.py!}
    ```

These dependencies will be executed/solved the same way as normal dependencies. But their value (if they return any) won't be passed to your *path operation function*.

!!! tip
    Some editors check for unused function parameters, and show them as errors.

# Path Operation Configuration

There are several parameters that you can pass to your *path operation decorator* to configure it.

!!! warning
    Notice that these parameters are passed directly to the *path operation decorator*, not to your *path operation function*.

## Response Status Code

You can define the (HTTP) `status_code` to be used in the response of your *path operation*.

You can pass directly the `int` code, like `404`.

{!../../../docs_src/templates/tutorial001.py!}
```

!!! note
    Before FastAPI 0.108.0, Starlette 0.29.0, the `name` was the first parameter.

    Also, before that, in previous versions, the `request` object was passed as part of the key-value pairs in the context for Jinja2.

!!! tip
    By declaring `response_class=HTMLResponse` the docs UI will be able to know that the response will be HTML.

!!! note "Technical Details"

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test_main.py <span style="color: green; white-space: pre;">......                            [100%]</span>

<span style="color: green;">================= 1 passed in 0.03s =================</span>
```

```

`.add_task()` receives as arguments:

* A task function to be run in the background (`write_notification`).
* Any sequence of arguments that should be passed to the task function in order (`email`).
* Any keyword arguments that should be passed to the task function (`message="some notification"`).

## Dependency Injection