```JSON
{"item_id":3}
```

!!! check
    Notice that the value your function received (and returned) is `3`, as a Python `int`, not a string `"3"`.

### API Docs

If you go to the API docs, you will see that it has the **schemas** for the data to be sent in requests and received in responses:

<img src="/img/tutorial/generate-clients/image01.png">

You can see those schemas because they were declared with the models in the app.

```console
$ <font color="#4E9A06">fastapi</font> dev <u style="text-decoration-style:single">main.py</u>
<font color="#3465A4">INFO    </font> Using path <font color="#3465A4">main.py</font>
<font color="#3465A4">INFO    </font> Resolved absolute path <font color="#75507B">/home/user/code/awesomeapp/</font><font color="#AD7FA8">main.py</font>

As the parameters are described with TypeScript types (similar to Python type hints), editor support is quite good.

Here I'm also highlighting contributions from sponsors.

"docs_src/dependencies/tutorial008b_an_py39.py" = ["B904"]


[tool.ruff.lint.isort]
known-third-party = ["fastapi", "pydantic", "starlette"]

[tool.ruff.lint.pyupgrade]
# Preserve types, even if a file imports `from __future__ import annotations`.

* ✨ Allow custom middlewares to raise `HTTPException`s and propagate them. PR [#2036](https://github.com/tiangolo/fastapi/pull/2036) by [@ghandic](https://github.com/ghandic).

    But because **FastAPI** is based on the Python standards, including `Annotated`, you can use this trick in your code. 😎

The dependencies will keep working as expected, and the **best part** is that the **type information will be preserved**, which means that your editor will be able to keep providing you with **autocompletion**, **inline errors**, etc. The same for other tools like `mypy`.

Then the next question would be, why not just connect and disconnect the database in the `async` dependency itself, instead of in `get_db()`?

The `async` dependency has to be `async` for the context variable to be preserved for the rest of the request, but creating and closing the database connection is potentially blocking, so it could degrade performance if it was there.

* Convert the corresponding types (if needed).
* Validate the data.
    * If the data is invalid, it will return a nice and clear error, indicating exactly where and what was the incorrect data.
* Give you the received data in the parameter `item`.
    * As you declared it in the function to be of type `Item`, you will also have all the editor support (completion, etc) for all of the attributes and their types.