Each resource method (GET, POST, PUT, DELETE, PATCH) has to provide brief documentation for itself. There should be a description of what given resource is responsible for and how a client interprets it. This documentation should contain information on expected input parameters (GET) or body (POST, PUT, PATCH), required and optional parameters, the response a client should expect and possible error codes. Documentation should be compatible with swagger spec 2.0 and should be accessible under a well-known endpoint (e.g. service-host/swagger.json).