You can’t really change CLI output from an action directly, I’m afraid. But you can do one of the following:
declare (in your clispec file) and implement s.c. pipe command - it can be a script that reformats the output of your action; you can then use the action like request config ... | reformat
reimplement your action as a CLI command - you can reuse big part of the code, the advantage of a CLI command is that you can format it however you want; probably with some tricks in your clispec file you can even “override” the action so that the command is used when requested from CLI.