I built something like this for native application, so that I could get automated feedback loop for the agent instead of making screenshots manually etc. Problem I found is that AI agent understands nothing of the UI. If you tell it "Make buttons evenly spaced", sure it will space them evenly, but without care for the context they are placed in. You have to describe the image yourself and still you'll find it having hard time understanding what's going on. I very much abandoned the idea of AI driven UI development as it is not there yet. I tried with GPT 5.2. Maybe newer models have improved.

I use Claude Code Sonnet and Opus for this and it works pretty well. Not perfect but good enough. At some point, I will have but to go in and tweak layout but like 99% of the functionality and layout is done for me.