Returning something to caller via Public Web method

I’m experimenting with using Workflow on iOS to invoke a macro.

I’ve proven I can do it with Mobile Safari. So far so good (and using get HTTP method from Workflow is just a small step further on).

I would like the workflow to return something - perhaps some text or XML or HTML - to the invoker. Is this feasible? If so how would I do it?

I could, of course, use a communications file in DropBox. But that’s rather clunky.

Keyboard Maestro has no built in facility for this. You would have to use some sort of other message passing service (Dropbox or something lighter).