alt Hacker NewsThis is my experience too, but with all other aspects of the application. If you only loosely describe it, it comes out as a mess. You have to know what you're building to get the LLM to actually build something decent. I don't think this is purely a visual or design constraint.
When I'm using agents for programming, I can have a AGENTS.md outlining exactly what requirements, guidelines and constraints all the code need to follow, and the agent (codex in my case) will pretty much nail that.
I've tried doing the same for design work, just really outlining exactly how the UI and UX needs to look and work, but for some reason it struggles a whole bunch with it, regardless of how clear I am. Maybe it's I'm just worse at explaining and describing what UI and UX I'm actually after though, I suppose.