Earlier quoted context omitted.
or just present it with the list of legal moves and force it to pick from said list.
I imagine there are points in a chess game, especially early on, where that list could have hundreds of moves - could use up a fair amount of tokens.
That's 20 moves. the size grows a bit in the early middle game, but then drops again in the endgame. There do exist rather artificial positions with more than 200 legal moves, but the average number of legal moves in a position is around 40.