How do you trace an ISG REST Web Service call?

I'm making a web service call, to the REST BOM structure exploder endpoint, deployed in ISG. The service fires successfully but it returns a parameter error.

However, when I call the same PL/SQL from the database, using the same parameters, it returns data without error. Now, I want to do a trace on the ISG endpoint, to see what data ISG is passing to the PL/SQL.

My question is "how do you trace an ISG REST Web Service request? " The logs from ISG administration are useless.

Any help is greatly appreciated

Thanks