If you are talking about JBoss EAP 6 I think you should have a subscription, in that case you can ask to RH Support.
As I already mentioned, I tried it in AS 5 (with EJB and interfaces into an EAR archive).
I think you don't need descriptors..
At any rate my ejb-jar.xml was:
<?xml version="1.0" encoding="UTF-8"?>
<ejb-jar xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://java.sun.com/xml/ns/javaee" xmlns:ejb="http://java.sun.com/xml/ns/javaee/ejb-jar_3_0.xsd" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/ejb-jar_3_0.xsd" version="3.0">
<display-name>MySampleSession</display-name>
<ejb-client-jar>MySessionClient.jar</ejb-client-jar>
</ejb-jar>