This is not a limitation of **FastAPI**, it's part of the HTTP protocol.

///

## Recap { #recap }

```
X-Token: foo
X-Token: bar
```

The response would be like:

```JSON
{
    "X-Token values": [
        "bar",
        "foo"
    ]
}
```

## Recap { #recap }

Declare headers with `Header`, using the same common pattern as `Query`, `Path` and `Cookie`.

This is not a limitation of **FastAPI**, it's part of the HTTP protocol.

///

## Recap { #recap }

///

```Python hl_lines="1"
async def needy_dependency(fresh_value: str = Depends(get_value, use_cache=False)):
    return {"fresh_value": fresh_value}
```

////

## Recap { #recap }

Apart from all the fancy words used here, the **Dependency Injection** system is quite simple.

Just functions that look the same as the *path operation functions*.

<img src="/img/tutorial/path-operation-configuration/image04.png">

Check how deprecated and non-deprecated *path operations* look like:

<img src="/img/tutorial/path-operation-configuration/image05.png">

## Recap { #recap }

As these keys may not necessarily be part of the OpenAPI specification, some OpenAPI tools, for example [the OpenAPI validator](https://validator.swagger.io/), may not work with your generated schema.

///

## Recap { #recap }

You can use Pydantic's `Field` to declare extra validations and metadata for model attributes.

        "tax": 3.2
    }
}
```

instead of:

```JSON
{
    "name": "Foo",
    "description": "The pretender",
    "price": 42.0,
    "tax": 3.2
}
```

## Recap { #recap }

You can add multiple body parameters to your *path operation function*, even though a request can only have a single body.

So, `0.5` would be a valid value. But `0.0` or `0` would not.

And the same for <abbr title="less than"><code>lt</code></abbr>.

{* ../../docs_src/path_params_numeric_validations/tutorial006_an_py39.py hl[13] *}

## Recap { #recap }

And all these thousands of *path operations* can be as small as 3 lines:

{* ../../docs_src/security/tutorial002_an_py310.py hl[30:32] *}

## Recap { #recap }

You can now get the current user directly in your *path operation function*.

We are already halfway there.

Но даже если вы заполните данные и нажмёте «Execute», поскольку UI документации работает с JavaScript, cookies отправлены не будут, и вы увидите сообщение об ошибке, как будто вы не указали никаких значений.

///

## Резюме { #recap }