I think the IDL should have a way how we can mark method declarations in a way that indicates that it generates multiple replies (i.e. sets the "more" flag). This is a fundamental property of a method calls, and usually very specific ones, hence I think this really deserves some kind of visibility in the interface files.

My proposal: maybe a method call that receives multiple replies could be suffixed with a "+" to indicate this fact, i.e.:

method Foobar(x: bool) -> (y: int)+

would indicate a function that returns a series of integers, one in each reply.

This would imply that method replies are "similar", i.e. that the return type declaration sensibly describes all replies the same. Which I think makes sense to expect.