There are other methods, including asking them to eg speak using the Google style guide rules, or to speak at 2/10 verbosity, or to speak as if they're talking to a very intelligent middle schooler, or to use simple sentences in subject verb object form
My favorite - reply like I do, review my previous messages to understand my tone and verbosity. As much as needed, as little as possible
It'll end up like that episode of Dr. Who where they get stranded in a lunar tour bus -- slowly starting to mimic you, and then it'll predict and replace you.