Wait, he's coming to the window, ... He's wagging his tail.

The tail is definitely wagging the dog here,

She's doing great. She's all shaved and has staples, but she's wagging her tail.

We had someone come the other day, and Alice was meeting two dogs and wagging her tail, and she came up to this person very quickly. She is still cautious and a little shy but makes friends quickly. She is confident, healthy, happy, social and loyal. She comes immediately when called, can be walked off-leash, knows basic commands and is very well-behaved. It's so encouraging.

I think the tail is definitely wagging the dog here.

If his tail is wagging, he likes you. You're either a friend or a relative, ... But if his tail is not wagging, you better watch out.