He backed them and wanted to force everyone to sign of have them be jailed.
Plus when he saw how they were jailed, he immediately was like "oh it's your fault for not listening to me".
I think they did a good job not making Tony a complete ass, but neither team was "right" in the endexcept for #TeamCap
Tony was clearly not very okay with it because unlike Cap he mostly tried to get everyone on the same page. It was his ego that undid any semblance of sympathetic admission with his co-mates since he faces his fuck up head-on despite not admitting towards his mistake, mostly because he's a little too proud of admitting his self-centered guilt. That said he backed the accords not only because he believed it was the right thing to do but because he worried that without them the team would fall apart. Ross is the one who wanted them jailed but Tony was the one who wanted them to either stay out of it or just sign the accords before Ross started forcing his hand in issuing the hard ultimatums. That's why Cap acknowledges that Tony probably cares more about the Avengers than he does, but that he'd be there for them if they ever need him.