A developer's experience of an API and its client libraries can make the difference between them building on a project and giving up in frustration. If you develop an API client library, you'll learn what you can do to get it out of the way so developers can spend mental energy on putting together exciting projects, not fighting with tools. If you work with web APIs, you'll learn about factors to consider when you're choosing a framework to use. Either way, you'll learn about best practices--code-related and not--that make the difference between fun and easy development and a frustrating slog.