A written agreement sounds heavier than it needs to be. One page is enough. Write it together, revisit it as your child and the tools change, and keep consequences proportionate. The Australian eSafety Commissioner recommends treating controls as supports for learning and combining them with conversation and supervision.
Cover five boundaries: use only services allowed for the child's age and account; do not enter sensitive personal information; follow school and assessment rules; disclose meaningful AI help; and get family agreement before publishing a name, image, voice or project. Add when an adult should stay nearby and what to do when the tool produces something upsetting or unsafe.
A plain example: "We use age-appropriate AI accounts with family settings on. We do not share private information. Schoolwork follows the teacher's rules, and meaningful AI help is disclosed. For personal projects, you make the decisions and can explain the result. We ask each other before anything becomes public, and you can bring us any strange or upsetting output without being in trouble."
The next step, if you want it: a free family assessment — about 3 minutes, one named profile, every source linked.