The HTTP specification specifies how to retrieve and update resources. Resources are identified using a URI and must be linked to each other, so all data must be accessible from the root URL of the service, as well as the pages on the website. This is what you need to document the media types that you transmit via cable.
If you take this approach and reuse media types through services, you only need to document the media type once, and it will be applicable to all services.
After you have completed these steps, there is really nothing left for the WADL document.
If you want to do REST, you cannot use WADL to generate code for generating clients, as this creates a tight connection between the client and the server. If this is normal with you, fine, but just understand that you are not performing REST and therefore you will not understand some of the benefits of REST.