I have tried several solutions mentioned over web, unfortunately without any success. In my project, I have two interfaces(xml/json) for each service. Adding mex endpoints or binding configurations did not helped at all. But, I have noticed, I get this error only when running project with *.svc.cs or *.config file focused. When I run project with IService.cs file focused (where interfaces are defined), service is added without any errors. This is really strange and in my opinion conclusion is bug in Visual Studio 2013. I reproduced same behaviour on several machines(even on Windows Server machine). Hope this helps someone.