 <p>Before I give my explanation, let me say that most pure REST extremists will deride it to the ends of the earth. I don't agree with them, as i'd rather get something done, but just so you know.</p> <p>WADL is a description of a web service API, a little like WSDL is for SOAP type web services, that is designed to be more in tune with RESTful interfaces (something WSDL is poor at).</p> <p>It's primary usage in my experience is to allow you to generate client code that can call the service (handy if it's a very large API, which literally saves hours of work). It also serves the purpose of documenting a REST-like interface.</p>