FastAPI emerges as a modern Python framework that leverages type hints for automatic data validation and documentation. Unlike Django's full-stack approach or Flask's simplicity, FastAPI specializes in building APIs with exceptional speed and reduced boilerplate code. The framework automatically generates interactive documentation, making code self-documenting.

Developers should consider FastAPI when building API-centric services where performance matters or when automatic documentation is valuable. The framework uses Pydantic models for data validation and dependency injection, streamlining development workflows. Installation requires Python 3.7+ and benefits from using the standard extras package, which includes the Uvicorn ASGI server.

A practical example demonstrates building a To-Do list API with full CRUD operations, showcasing path parameters, request bodies, and error handling. The code reveals FastAPI's core patterns: decorators define routes, Pydantic models validate data, and dependency injection manages common parameters. This combination of features makes FastAPI particularly effective for microservices and modern web applications where rapid development and clear documentation are priorities.