APIs
====

API applications expose Julee :doc:`use cases </architecture/clean_architecture/use_cases>` via REST endpoints using FastAPI.

APIs execute use cases directly for synchronous operations, or trigger :doc:`worker <worker>` :doc:`pipelines </architecture/solutions/pipelines>` via Temporal client for asynchronous operations. Use cases receive dependencies (:doc:`repositories </architecture/clean_architecture/repositories>`, :doc:`services </architecture/clean_architecture/services>`) via FastAPI's :doc:`dependency injection </architecture/clean_architecture/dependency_injection>`. Request and response models are Pydantic models separate from :doc:`domain models </architecture/clean_architecture/entities>`, providing API contracts that can evolve independently.

:doc:`UIs <ui>` interact with the system exclusively through the API. :doc:`CLIs <cli>` can also call APIs, though they more commonly invoke use cases directly.