The JMX console does display the MBeanOperationInfo, which is the name and description. Unfortunately, there's no way to specify the default values except by adding them in the description.
Potentially, JBoss could extend MBeanParameterInfo and add a default value field, which would come from the XMBean XML. It's not likely difficult to do this. If you can get this to work, create a patch and JIRA issue and it will get added.