Option would be,once you do wm.b2b.edi:convertToString (which gives output string edidata) and then explicity invoke wm.b2b.edi:convertToValues set validate to yes (it validates against EDIFFSchema) and based on the result vars isValid,errorArray branching, you can perform next steps add Envelopes, routing to TN etc…else notify errors.
HTH,
RMg
#Integration-Server-and-ESB#webMethods#edi