When testing a WCF application locally, take the time to publish it to a site hosted in IIS and not just a virtual directory.

Duh. Don't make this mistake. Otherwise you'll get an error such as:

There was an error downloading metadata from the address. Please verify that you have entered a valid address.

 
 

With suggestions for what the problem could be such as:

• the metadata exchange mex endpoint is not defined
• metadata exchange is not enabled
• you are using the wrong address
• you are being blocked by some security setting

 
 

...when you attempt to reference in the service at another application in Visual Studio 2013.