Documentation is the essential building block for any API, and the number one pain point for developers when consuming an API. Documentation is how you translate the surface area of your API resources and capabilities into something human developers will understand and be able to use.
Your API documentation should be generated from your OpenAPI definition. Your OpenAPI should contain all of the paths, methods, parameters, operations, responses, examples, and errors needed to publish a robust and useful set of documentation. The quality of your documentation will depend on the collaboration between product and engineering when it comes to producing your OpenAPI.
The documentation for your API is a visual representation of your team and backend systems, but reduced down to a set of coherent and meaningful API operations. Your API documentation is the first impression you will make on your API consumers, and the accuracy and coherence of your summaries, descriptions, as well as the overall design of your API will have an outsized impact on how your documentation is received by API consumers.