https://wccftech.com/your-iphone-will-send-you-a-notification-if-someone-plants-an-airtag-on-you-for-tracking/

Privacy is at the core of Apple and the AirTag is built with that in mind. You will know if someone is trying to track you with an AirTag.

AirTag is a tracker which Apple fans have been waiting for. Not only it is great for tracking, but the Find My network makes the entire tracking process that much precise. But this also means that someone can play foul on you and plant a track on you for tracking your whereabouts. This is something which is bound to happen with someone and Apple knew about it from the get go.