Any additional JSON schema data.
            """
        ),
    ] = None,
    **extra: Annotated[
        Any,
        Doc(
            """
            Include extra fields used by the JSON Schema.
            """
        ),
        deprecated(
            """
            The `extra` kwargs is deprecated. Use `json_schema_extra` instead.
            """
        ),
    ],
) -> Any:

**FastAPI** will **extract** the data for **each field** from the **headers** in the request and give you the Pydantic model you defined.

## Check the Docs { #check-the-docs }

You can see the required headers in the docs UI at `/docs`:

<div class="screenshot">
<img src="/img/tutorial/header-param-models/image01.png">
</div>

## Forbid Extra Headers { #forbid-extra-headers }

again.  The Mock Turtle went on.

  `We had the best of educations--in fact, we went to school
every day--'

  `I'VE been to a day-school, too,' said Alice; `you needn't be
so proud as all that.'

  `With extras?' asked the Mock Turtle a little anxiously.

  `Yes,' said Alice, `we learned French and music.'

  `And washing?' said the Mock Turtle.

  `Certainly not!' said Alice indignantly.

`Header` has a little extra functionality on top of what `Path`, `Query` and `Cookie` provide.

Most of the standard headers are separated by a "hyphen" character, also known as the "minus symbol" (`-`).

But a variable like `user-agent` is invalid in Python.

So, by default, `Header` will convert the parameter names characters from underscore (`_`) to hyphen (`-`) to extract and document the headers.

Sebastián Ramírez <******@****.***> 1731896744 +0100

timothy <******@****.***> 1748612313 +0900

But even if you **fill the data** and click "Execute", because the docs UI works with **JavaScript**, the cookies won't be sent, and you will see an **error** message as if you didn't write any values.

///

## Forbid Extra Cookies { #forbid-extra-cookies }

In some special use cases (probably not very common), you might want to **restrict** the cookies that you want to receive.

Guillaume Nodet <******@****.***> 1729859506 +0200

Sebastián Ramírez <******@****.***> 1731896744 +0100

Sebastián Ramírez <******@****.***> 1731896744 +0100