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:

=== "Python 3.9+"

    ```Python hl_lines="16"
    {!> ../../../docs_src/dependencies/tutorial012_an_py39.py!}
    ```

=== "Python 3.8+"

!!! info
    A "bearer" token is not the only option.

    But it's the best one for our use case.

    And it might be the best for most use cases, unless you are an OAuth2 expert and know exactly why there's another option that suits better your needs.

    In that case, **FastAPI** also provides you with the tools to build it.

In this case, it would use the certificate for `someapp.example.com`.

<img src="/img/deployment/https/https03.svg">

The client already **trusts** the entity that generated that TLS certificate (in this case Let's Encrypt, but we'll see about that later), so it can **verify** that the certificate is valid.

# OpenAPI

There are several utilities to handle OpenAPI.

    !!! tip
        Prefer to use the `Annotated` version if possible.

    ```Python hl_lines="19-21"
    {!> ../../../docs_src/body_multiple_params/tutorial001.py!}
    ```

!!! note
    Notice that, in this case, the `item` that would be taken from the body is optional. As it has a `None` default value.

## Multiple body parameters

Of course, there are some cases where there's no problem in running the previous steps multiple times, in that case, it's a lot easier to handle.

!!! tip
    Also, keep in mind that depending on your setup, in some cases you **might not even need any previous steps** before starting your application.

    In that case, you wouldn't have to worry about any of this. 🤷

### Examples of Previous Steps Strategies

## Use Case

Let's start with an example **use case** and then see how to solve it with this.

Let's imagine that you have some **machine learning models** that you want to use to handle requests. 🤖

* Implement and use well-known cryptographic tools, like Passlib and JWT tokens, etc.
* Add more granular permission controls with OAuth2 scopes where needed.
* ...etc.

Nevertheless, you might have a very specific use case where you really need to disable the API docs for some environment (e.g. for production) or depending on configurations from environment variables.

## Conditional OpenAPI from settings and env vars

```

By declaring a *path operation function* parameter with the type being the `Request` **FastAPI** will know to pass the `Request` in that parameter.

!!! tip
    Note that in this case, we are declaring a path parameter beside the request parameter.

    So, the path parameter will be extracted, validated, converted to the specified type and annotated with OpenAPI.

```

Calling this program outputs:

```
John Doe
```

The function does the following:

* Takes a `first_name` and `last_name`.
* Converts the first letter of each one to upper case with `title()`.
* <abbr title="Puts them together, as one. With the contents of one after the other.">Concatenates</abbr> them with a space in the middle.

```Python hl_lines="2"
{!../../../docs_src/python_types/tutorial001.py!}