### Check the docs

Now, if you check the docs, they will show all the additional metadata:

<img src="/img/tutorial/metadata/image02.png">

### Order of tags

The order of each tag metadata dictionary also defines the order shown in the docs UI.

For example, even though `users` would go after `items` in alphabetical order, it is shown before them, because we added their metadata as the first dictionary in the list.

## OpenAPI URL

If you don't care about any of these terms and you just need to add security with authentication based on username and password *right now*, skip to the next chapters.

## OAuth2

OAuth2 is a specification that defines several ways to handle authentication and authorization.

It is quite an extensive specification and covers several complex use cases.

It includes ways to authenticate using a "third party".

# Parámetros de Cookie

Puedes definir parámetros de Cookie de la misma manera que defines parámetros de `Query` y `Path`.

## Importar `Cookie`

Primero importa `Cookie`:

{* ../../docs_src/cookie_params/tutorial001_an_py310.py hl[3]*}

## Declarar parámetros de `Cookie`

Luego declara los parámetros de cookie usando la misma estructura que con `Path` y `Query`.

# Handling Errors

There are many situations in which you need to notify an error to a client that is using your API.

This client could be a browser with a frontend, a code from someone else, an IoT device, etc.

You could need to tell the client that:

* The client doesn't have enough privileges for that operation.
* The client doesn't have access to that resource.
* The item the client was trying to access doesn't exist.
* etc.

Underneath, in the ASGI technical specification, this is part of the <a href="https://asgi.readthedocs.io/en/latest/specs/lifespan.html" class="external-link" target="_blank">Lifespan Protocol</a>, and it defines events called `startup` and `shutdown`.

/// info

You might want to try their services and follow their guides:

* <a href="https://docs.platform.sh/languages/python.html?utm_source=fastapi-signup&utm_medium=banner&utm_campaign=FastAPI-signup-June-2023" class="external-link" target="_blank">Platform.sh</a>

{!../../docs_src/path_operation_advanced_configuration/tutorial004.py!}
```

## Additional Responses

You probably have seen how to declare the `response_model` and `status_code` for a *path operation*.

That defines the metadata about the main response of a *path operation*.

You can also declare additional responses with their models, status codes, etc.

➕ 🌐 💂‍♂ ⚒ ⚪️➡️ 💃 (🔌 **🎉 🍪**).

🌐 🏗 ♻ 🧰 & 🦲 👈 ⏩ 🛠️ ⏮️ 👆 ⚙️, 📊 🏪, 🔗 & ☁ 💽, ♒️.

### 🔗 💉

FastAPI 🔌 📶 ⏩ ⚙️, ✋️ 📶 🏋️ <abbr title='also known as "components", "resources", "services", "providers"'><strong>🔗 💉</strong></abbr> ⚙️.

* 🔗 💪 ✔️ 🔗, 🏗 🔗 ⚖️ **"📊" 🔗**.
* 🌐 **🔁 🍵** 🛠️.
* 🌐 🔗 💪 🚚 💽 ⚪️➡️ 📨 &amp; **↔ ➡ 🛠️** ⚛ &amp; 🏧 🧾.
* **🏧 🔬** *➡ 🛠️* 🔢 🔬 🔗.

加上来自 Starlette（包括 **session cookie**）的所有安全特性。

所有的这些都是可复用的工具和组件，可以轻松与你的系统，数据仓库，关系型以及 NoSQL 数据库等等集成。



### 依赖注入

FastAPI 有一个使用非常简单，但是非常强大的<abbr title='也叫做 "components", "resources", "services", "providers"'><strong>依赖注入</strong></abbr>系统。

* 甚至依赖也可以有依赖，创建一个层级或者**“图”依赖**。
* 所有**自动化处理**都由框架完成。
* 所有的依赖关系都可以从请求中获取数据，并且**增加了路径操作**约束和自动文档生成。
* 即使在依赖项中被定义的*路径操作* 也会**自动验证**。
* 支持复杂的用户身份认证系统，**数据库连接**等等。