When using the REST API classes for building services on a spec-first approach, the implementation class methods are usually built this format:

ClassMethod <method-name>(body As %DynamicObject) As %Stream.Object

But sometimes it keeps building the endpoint implementation method like this:

ClassMethod <method-name>(body As %Stream.Object) As %DynamicObject

It has been a problem because the rest of my implementation rely on the fact that the "body" object is a DynamicObject.