There are 2 main differences from a normal *path operation*:

* It doesn't need to have any actual code, because your app will never call this code. It's only used to document the *external API*. So, the function could just have `pass`.

### Include the custom docs { #include-the-custom-docs }

Now you can create the *path operations* for the custom docs.

You can reuse FastAPI's internal functions to create the HTML pages for the docs, and pass them the needed arguments:

* `openapi_url`: the URL where the HTML page for the docs can get the OpenAPI schema for your API. You can use here the attribute `app.openapi_url`.
* `title`: the title of your API.

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

///

When we create an instance of the `OAuth2PasswordBearer` class we pass in the `tokenUrl` parameter. This parameter contains the URL that the client (the frontend running in the user's browser) will use to send the `username` and `password` in order to get a token.

                    pass = userInfo.substring(i + 1);
                    break;
                }
            }
            user = userInfo.substring(u, i);
        }

        this.domain = dom != null ? dom : defDomain != null ? defDomain : "";
        this.username = user != null ? user : defUser != null ? defUser : "";

		if actualErr != nil && testCase.expectedError == nil {
			t.Errorf("Test %d: %s: Expected to pass, but failed with: error %s.", i, instanceType, actualErr.Error())
			continue
		}
		if actualErr == nil && testCase.expectedError != nil {

            proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
            proxy_set_header X-Forwarded-Proto $scheme;
            proxy_set_header X-NginX-Proxy true;

            # This is necessary to pass the correct IP to be hashed
            real_ip_header X-Real-IP;

            proxy_connect_timeout 300;
            
            # To support websocket
            proxy_http_version 1.1;

...makes the parameter optional, with a default value of `None`, the same as:


```Python
q: str | None = None
```

But the `Query` version declares it explicitly as being a query parameter.

Then, we can pass more parameters to `Query`. In this case, the `max_length` parameter that applies to strings:

```Python
q: str | None = Query(default=None, max_length=50)
```

For that you need to access the request directly.

{* ../../docs_src/using_request_directly/tutorial001.py hl[1,7:8] *}

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.

///

## Recap { #recap }

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

  }

  // TODO(cpovirk): Use standard Javadoc form for SimpleForwarding* class and constructor
  /**
   * A simplified version of {@link ForwardingListenableFuture} where subclasses can pass in an
   * already constructed {@link ListenableFuture} as the delegate.
   *
   * @since 9.0
   */
  public abstract static class SimpleForwardingListenableFuture<V extends @Nullable Object>