You put it on top of a function. Like a pretty decorative hat (I guess that's where the term came from).

A "decorator" takes the function below and does something with it.

In our case, this decorator tells **FastAPI** that the function below corresponds to the **path** `/` with an **operation** `get`.

It is the "**path operation decorator**".

///

You can also use the other operations:

* `@app.post()`
* `@app.put()`

    * Zuerst werden die Router-Abhängigkeiten ausgeführt, dann die [`dependencies` im Dekorator](dependencies/dependencies-in-path-operation-decorators.md){.internal-link target=_blank} und dann die normalen Parameterabhängigkeiten.

# 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`.

                *path operation*.

                Read more about it in the
                [FastAPI docs for Dependencies in path operation decorators](https://fastapi.tiangolo.com/tutorial/dependencies/dependencies-in-path-operation-decorators/).
                """
            ),
        ] = None,
        summary: Annotated[
            Optional[str],
            Doc(
                """

                *path operation*.

                Read more about it in the
                [FastAPI docs for Dependencies in path operation decorators](https://fastapi.tiangolo.com/tutorial/dependencies/dependencies-in-path-operation-decorators/).
                """
            ),
        ] = None,
        summary: Annotated[
            Optional[str],
            Doc(
                """

    response = client.get("/decorator-depends/?q=foo")
    assert response.status_code == 200
    assert response.json() == {"in": "decorator-depends"}


def test_decorator_depends_q_foo_skip_100_limit_200():
    response = client.get("/decorator-depends/?q=foo&skip=100&limit=200")
    assert response.status_code == 200
    assert response.json() == {"in": "decorator-depends"}


def test_router_depends():

/// tip

Note that, much like [dependencies in *path operation decorators*](dependencies/dependencies-in-path-operation-decorators.md){.internal-link target=_blank}, no value will be passed to your *path operation function*.

///

The end result is that the item paths are now:

* `/items/`
* `/items/{item_id}`

# Global Dependencies

For some types of applications you might want to add dependencies to the whole application.

Similar to the way you can [add `dependencies` to the *path operation decorators*](dependencies-in-path-operation-decorators.md){.internal-link target=_blank}, you can add them to the `FastAPI` application.

In that case, they will be applied to all the *path operations* in the application:

//// tab | Python 3.9+

```Python hl_lines="16"

                          "config": "/apis/networking.istio.io/v1alpha3/namespaces/default/virtual-service/bookinfo"
                        }
                      }
                    },
                    "decorator": {
                      "operation": "productpage.default.svc.cluster.local:9080/productpage"
                    }
                  },
                  {
                    "match": {

**FastAPI** includes utilities for all these OAuth2 authentication flows in `fastapi.security.oauth2`.

## `Security` in decorator `dependencies`