I think the tail is definitely wagging the dog here.

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.

A lot of people come here, and when they open the (front) door the dog starts running and tail-wagging.

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.

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