Apple has consistently said that the AirTag is meant to track items, not people or pets. The biggest downside is your pet needs to be in range of a device in the Find My network so its location can be tracked. That means it’s not perfect, OK, I’m good with that.
I don’t rely on the AirTag as the only way to bring my dog home if he ever gets lost. Rex is microchipped, has a traditional dog tag with my phone number, and his new AirTag. He’s also a good boy and comes when he’s called.
Here’s where I got the AirTag slide on dog collar attachment: