This document provides information on creating usable REST APIs. It discusses principles like following best practices, making APIs learnable and efficient for users, and avoiding exposing implementation details. The document also provides examples of API design choices around topics like versioning, pagination, and allowing asynchronous operations. It emphasizes that there are no single right answers and each API has different needs, so copying approaches from other projects without thought is the wrong approach. The overall message is to thoughtfully design APIs around usability and the needs of developers using the API.