Given just a bit of knowledge about your application, what a command does should be obvious by reading the command. For example, "delete window mywindow" is much better than "dw".
Similarly, given a bit of knowledge about your application and a grounding in ARexx, any syntactic errors should be obvious from reading the command. For example, that "rexx-do-on-exit exitmacro thisrexx" requires that the command ("rexx-do-on-exit") be quoted, and that the two arguments be turned into a single string with double quotes around it, is not obvious.
On to evaluations, back to consistent, or up to goals of a design.
Mike W. Meyer