Question: Is there a rule that states, the player who wants to stop the Charleston must announce it, or does someone in the group ask, “does everyone want to continue?”

Answer:  It is the responsibility of the player who wants to stop the Charleston to announce their intentions. If a player is thinking of stopping the Charleston, it is good to get in the habit of letting everyone know during the first left. You might say something like, “Please go slowly as I might wan to stop the Charleston”. (See also ID148, Stopping the Charleston, is it too late)

Source:  Mah Jongg Made Easy 2024, pg. 13, para. 1