This is normally called a **webhook**.

## Webhooks steps

The process normally is that **you define** in your code what is the message that you will send, the **body of the request**.

You also define in some way at which **moments** your app will send those requests or events.

And **your users** define in some way (for example in a web dashboard somewhere) the **URL** where your app should send those requests.

## Documentation Response description - OpenAPI

To define the description of the response, shown in the docs UI, read the docs for [Tutorial - Path Operation Configurations - Response description](../tutorial/path-operation-configuration.md#response-description){.internal-link target=_blank}.

### OpenAPI support

OpenAPI doesn't support a way to declare a *path parameter* to contain a *path* inside, as that could lead to scenarios that are difficult to test and define.

Nevertheless, you can still do it in **FastAPI**, using one of the internal tools from Starlette.

And the docs would still work, although not adding any documentation telling that the parameter should contain a path.

**FastAPI** will know that it can use this dependency to define a "security scheme" in the OpenAPI schema (and the automatic API docs).

!!! info "Technical Details"

# Body - Nested Models

With **FastAPI**, you can define, validate, document, and use arbitrarily deeply nested models (thanks to Pydantic).

## List fields

You can define an attribute to be a subtype. For example, a Python `list`:

=== "Python 3.10+"

    ```Python hl_lines="12"
    {!> ../../../docs_src/body_nested_models/tutorial001_py310.py!}
    ```

=== "Python 3.8+"

    ```Python hl_lines="14"

## Import Couchbase components

For now, don't pay attention to the rest, only the imports:

```Python hl_lines="3-5"
{!../../../docs_src/nosql_databases/tutorial001.py!}
```

## Define a constant to use as a "document type"

We will use it later as a fixed field `type` in our documents.

This is not required by Couchbase, but is a good practice that will help you afterwards.

```Python hl_lines="9"

# Lifespan Events

You can define logic (code) that should be executed before the application **starts up**. This means that this code will be executed **once**, **before** the application **starts receiving requests**.

The same way, you can define logic (code) that should be executed when the application is **shutting down**. In this case, this code will be executed **once**, **after** having handled possibly **many requests**.

# Eventos de vida útil

Você pode definir a lógica (código) que poderia ser executada antes da aplicação **inicializar**. Isso significa que esse código será executado **uma vez**, **antes** da aplicação **começar a receber requisições**.

Do mesmo modo, você pode definir a lógica (código) que será executada quando a aplicação estiver sendo **encerrada**. Nesse caso, este código será executado **uma vez**, **depois** de ter possivelmente tratado **várias requisições**.

    """
    API key authentication using a query parameter.

    This defines the name of the query parameter that should be provided in the request
    with the API key and integrates that into the OpenAPI documentation. It extracts
    the key value sent in the query parameter automatically and provides it as the
    dependency result. But it doesn't define how to send that API key to the client.

    ## Usage

## Singular values in body

The same way there is a `Query` and `Path` to define extra data for query and path parameters, **FastAPI** provides an equivalent `Body`.

For example, extending the previous model, you could decide that you want to have another key `importance` in the same body, besides the `item` and `user`.