The best replacement for wsdl is soap.

The best alternatives to wsdl are rated as following:
★★★★★  soap
★★★★  wadl
★★★★  xsd
★★★★  rest
★★  asmx
★  uddi
★  single wsdl
★  svcutil
★  api
★  mex
★  idl
★  schema
  wsdl
  wsdd
  disco
  web service
  xml schema

Your alternative for wsdl is not listed? Suggest!
Speaking about wsdl, one probably shouldn't forget about xsd.

Other search terms related to wsdl and their ratings are:
★★★★★ xsd
★★★ soap
★★ service
★★ rest
★★ soap header
★ at least one service definition needs to be provided
uddi
You have in mind a companion for wsdl and it is not yet here? Propose!



Google Trends

Scale is based on the average worldwide traffic of wsdl in all years. Click on graph for more.
wsdl
soap
wadl