Several tools facilitate the automatic generation of API documentation. Popular options include: Swagger (now part of the OpenAPI Initiative): This tool auto-generates documentation from API definitions, providing a user-friendly interface and interactive capabilities. Doxygen: Primarily for C++, but it supports other languages. It generates documentation from source code annotations. Javadoc: For Java-based APIs, Javadoc generates documentation based on comments embedded within the source code. Slate: While not entirely automatic, Slate provides a clean, intuitive platform for creating API documentation with markdown. The choice of tool largely depends on the API's language, desired output format, and specific documentation needs.