A computer system automatically generates service documentation based on usage of a web service. The computer system captures network traffic including actual requests to a service endpoint of the web service and actual responses from the service endpoint of the web service. The captured network traffic can be analyzed using machine learning to determine one or more operations that are available at the service endpoint, input arguments that are accepted by the service endpoint, and output arguments that are provided by the service endpoint. The computer system can automatically generate service documentation for the web service based on metadata that identifies the operations, the input arguments, and the output arguments.