Apple has released support information, “What to do if you find an AirTag or get an alert that an AirTag is with you.”
Put the lost AirTag in Lost Mode and you will be notified automatically when a device on your network detects AirTag.
The person who finds it taps the NFC-enabled iPhone or smartphone on the white side of the AirTag and keeps hitting it.
And when you tap the displayed notification, it seems that a website that provides AirTag information such as serial number will open.
It seems that these can be done by setting so that the contact information can be confirmed.
