Integration Server 10.3 | Web Services Developer’s Guide | SOAP Message Exchange Patterns | How Adding Response Headers or Faults Affect In-Only MEP Operations
 
How Adding Response Headers or Faults Affect In-Only MEP Operations
If you have an In-Only MEP operation, the MEP type changes if you add a response header or a fault to the operation.
*If you add a response header to an In-Only MEP operation, the MEP changes to In-Out MEP.
*If you add a fault to an In-Only MEP operation, the MEP changes to Robust In-Only MEP.