Vinyl Siding intersects chimney

I’ve attached a few photo’s to help. I did some reading through installation instructions and do not see specific instructions for the intersection between vinyl siding chimney vertically. Does anyone have a good book or website reference for this? Though you could caulk this, that seems like a short-term solution to a long-term problem.

Is this a 3-sided brick enclosure for just a metal vent?
What is it venting?

Yes, it is, there’s a metal vent for the gas fireplace.

Well, I sure would be looking to call out any areas that might be able allow water intrusion in the wall assembly and I would also want to check what is supporting the brick on the back side of the chimney enclosure.

Quite an expensive vent enclosure.

Thank you for your comments.