In the last few years, RESTful web services have become as ubiquitous as SOAP in the early 2000s. You look anywhere in the tech community, you will notice someone somewhere is either talking or doing something with REST APIs or microservices. In spite of its immense popularity, REST lacks any type of standard other than a few guiding principles. REST doesn’t have anything similar to Web Service Definition Language (WSDL). WSDL is used for describing SOAP operations, messages, and also for generating client code.