Hi Manjiri,
you don't need a custom action block. I also use xml as output.
You have to use XDSs to generate a valid XML-document.
Example to use XSDs in MII:
http://scn.sap.com/community/manufacturing/mii/blog/2014/10/01/sap-mii-illuminator-document-xsd
Best Regards,
Matthias
