/// tip

You don't have to add metadata for all the tags that you use.

///

### Use your tags { #use-your-tags }

Use the `tags` parameter with your *path operations* (and `APIRouter`s) to assign them to different tags:

{* ../../docs_src/metadata/tutorial004.py hl[21,26] *}

/// info

Read more about tags in [Path Operation Configuration](path-operation-configuration.md#tags){.internal-link target=_blank}.

///

So, in our example, we can make `tags` be specifically a "list of strings":

{* ../../docs_src/body_nested_models/tutorial002_py310.py hl[12] *}

## Set types { #set-types }

But then we think about it, and realize that tags shouldn't repeat, they would probably be unique strings.

And Python has a special data type for sets of unique items, the `set`.

Then we can declare `tags` as a set of strings:

**FastAPI** provides the same `starlette.status` as `fastapi.status` just as a convenience for you, the developer. But it comes directly from Starlette.

///

## Tags { #tags }

You can add tags to your *path operation*, pass the parameter `tags` with a `list` of `str` (commonly just one `str`):

{* ../../docs_src/path_operation_configuration/tutorial002_py310.py hl[15,20,25] *}

## Documentation Tags - OpenAPI { #documentation-tags-openapi }

To add tags to your *path operations*, and group them in the docs UI, read the docs for [Tutorial - Path Operation Configurations - Tags](../tutorial/path-operation-configuration.md#tags){.internal-link target=_blank}.

### Add some custom `tags`, `responses`, and `dependencies` { #add-some-custom-tags-responses-and-dependencies }

We are not adding the prefix `/items` nor the `tags=["items"]` to each *path operation* because we added them to the `APIRouter`.

<img src="/img/tutorial/generate-clients/image05.png">

## FastAPI App with Tags { #fastapi-app-with-tags }

In many cases, your FastAPI app will be bigger, and you will probably use tags to separate different groups of *path operations*.

For example, you could have a section for **items** and another section for **users**, and they could be separated by tags:

{* ../../docs_src/generate_clients/tutorial002_py39.py hl[21,26,34] *}

  features:
  - content.code.annotate
  - content.code.copy
  - content.footnote.tooltips
  - content.tabs.link
  - content.tooltips
  - navigation.footer
  - navigation.indexes
  - navigation.instant
  - navigation.instant.prefetch
  - navigation.instant.progress
  - navigation.path
  - navigation.tabs
  - navigation.tabs.sticky
  - navigation.top
  - navigation.tracking
  - search.highlight
  - search.share

{* ../../docs_src/websockets/tutorial003_py39.py hl[79:81] *}

To try it out:

* Open the app with several browser tabs.
* Write messages from them.
* Then close one of the tabs.

That will raise the `WebSocketDisconnect` exception, and all the other clients will receive a message like:

```
Client #1596980209979 left the chat
```

/// tip

```Python hl_lines="3  5-6"
{
    "name": "Baz",
    "description": None,
    "price": 50.2,
    "tax": 10.5,
    "tags": []
}
```

FastAPI is smart enough (actually, Pydantic is smart enough) to realize that, even though `description`, `tax`, and `tags` have the same values as the defaults, they were set explicitly (instead of taken from the defaults).

So, they will be included in the JSON response.

You can combine `dataclasses` with other type annotations in many different combinations to form complex data structures.

Check the in-code annotation tips above to see more specific details.

## Learn More { #learn-more }

You can also combine `dataclasses` with other Pydantic models, inherit from them, include them in your own models, etc.