API documentation is crucial for maintaining the functionality and usability of an API, as it prevents the chaos that ensues when developers leave or forget how an API works. The lack of documentation can lead to companies repeatedly building new API versions with no real improvements, simply because the original functionality cannot be remembered or replicated. Using OpenAPI from the outset can streamline this process by allowing for the creation of mock servers and contract testing, ensuring that APIs are built according to stakeholder needs and are reliably tested early in the development process. This approach not only saves time but also provides a solid foundation for API documentation, which can then be enhanced by technical writers to offer comprehensive, user-friendly guides. Overall, early implementation of OpenAPI and thorough documentation can prevent costly mistakes and ensure the efficient operation and evolution of APIs.