The primary focus of API documentation for developers is to provide clear and concise information on how to effectively interact with an Application Programming Interface. This includes information on endpoints, request/response formats, authentication methods, and usage examples. Well-structured API documentation enables developers to quickly understand how to integrate applications and helps reduce the learning curve associated with any API. Comprehensive documentation not only improves the usability of the API but also fosters adoption, reduces error rates, and enhances overall developer experience.