WSDL 2.0: www.w3.org/TR/wsdl20/ WADL www.w3.org/Submission/wadl/ XRD www.oasis-open.org/committees/download.php/35274/xrd-1.0-wd10.html All three can be used a REST API descriptors. What's the differences? I know this is a heated question, but I simply want a comparison, not a flame war :P