While using WS Provider if you want to set the value for SOAPFaultString and SOAPFaultDetail variable. Then you can create the PutContext variable for these variables in the Process Flow designer of the Provider and can further use these .
Create a Put Context Var activity in which we will store the value for variable SOAPFaultString and SOAPFaultDetail. The value for SOAPFaultString contains the error message and it should be string and value for SOAPFaultDetail variable should be a valid XML containing the code and message tags inside the root tag.
Structure of XML should be like below: