Ask, don't guess
Also called Never block on the human
A rule for the agent: when the answer changes what gets built and it can't find out for itself, stop and ask instead of quietly picking. People disagree about how often that should be.
Each silent guess is a decision you never saw. Each question stops you, and stops a long run dead. Both are real costs, and what settles it is mostly how hard the guess is to undo. If it's reversible, proceed and report. If it isn't, ask.
Say it to your agent
“If a decision is reversible, pick the simplest option, carry on, and list what you picked at the end. Stop and ask me first before anything you can't undo, and before any product choice the spec doesn't settle.”