Yes, he was a rat, no question. Showing up on Tony's and asking him those questions, calling the meeting, getting low ball bail after those guns were found in his club and he had a pistol on him......how could he not be a rat how they laid all that out in the show? The official book HBO put out (the cannon one that Chase signed off on) they state that he was indeed a rat in what's meant to be an official FBI report on Jimmy after he turned up with the rat in his mouth.