Joe Gregorio wrote a blogpost that asks if we need WADL, for describing REST services, and effectively WSDL. He argues that we do not need something as expressive as XSD every time we write a WSDL contract, and that we should avoid doing the same error with REST and WADL.
He introduces the concept of using MIME-type standards as the main part of your contract. For example, you would only have to tell that your service is a mail service via a MIME-type instead of creating a gigantic WSDL that describes the different ways you can interact with a mail server. Perhaps we should use this more when we create the contracts for our services?
For those of you who are unfamiliar with REST, I can recommend you reading this article.