# Using Dataclasses { #using-dataclasses }

FastAPI is built on top of **Pydantic**, and I have been showing you how to use Pydantic models to declare requests and responses.

But FastAPI also supports using <a href="https://docs.python.org/3/library/dataclasses.html" class="external-link" target="_blank">`dataclasses`</a> the same way:

{* ../../docs_src/dataclasses_/tutorial001_py310.py hl[1,6:11,18:19] *}

* `deprecated`: to mark all the *path operations* in a router as deprecated in OpenAPI.
* `include_in_schema`: to allow disabling all the *path operations* from showing in the OpenAPI schema.
* `callbacks`: OpenAPI callbacks that apply to all the *path operations* in this router.