# Security Tools

When you need to declare dependencies with OAuth2 scopes you use `Security()`.

But you still need to define what is the dependable, the callable that you pass as a parameter to `Depends()` or `Security()`.

There are multiple tools that you can use to create those dependables, and they get integrated into OpenAPI so they are shown in the automatic docs UI, they can be used by automatically generated clients and SDKs, etc.

And then, that system (in this case **FastAPI**) will take care of doing whatever is needed to provide your code with those needed dependencies ("inject" the dependencies).

This is very useful when you need to:

* Have shared logic (the same code logic again and again).
* Share database connections.

---

## Install FastAPI

The first step is to install FastAPI:

<div class="termy">

```console
$ pip install fastapi

---> 100%
```

</div>

!!! note
    When you install with `pip install fastapi` it comes with some default optional standard dependencies.

    If you don't want to have those optional dependencies, you can instead install `pip install fastapi-slim`.

* `fastapi-cli` - to provide the `fastapi` command.

When you install `fastapi` it comes these standard dependencies.

## `fastapi-slim`

If you don't want the extra standard optional dependencies, install `fastapi-slim` instead.

When you install with:

```bash
pip install fastapi
```

...it includes the same code and dependencies as:

You could **deploy a server** yourself using a combination of tools, you could use a **cloud service** that does part of the work for you, or other possible options.

I will show you some of the main concepts you should probably keep in mind when deploying a **FastAPI** application (although most of it applies to any other type of web application).