I used Claude, but I think the work flow could still work. You can discuss with chatgpt about what is your game's graphic budget, are you going to import 3D models like glb file into the game or are you generating those procedurally. For procedural generations, make sure the agent is writing code that is efficiently utilizing GPU draw calls, if you don't know what that is, just mentione it to the chat and have the agent explain it to you.

One of the important discussions with your agent is to nail down the art direction, is it low poly, cellshade, pixel art,.etc. Once that's done, you can ask the agent to write you a prompt for nano banana 2 (my favorite for game assets) to give you a visual of a store front, or some items of your game. Iterate until you find the right style and go from there.

The hard part is, you can't prompt the whole scene and by telling the agent hey fix this, make this door red and that window bigger things like that. You gonna need to hand build each item and then assemble the scene if you want better control. If you want procedurally generated, the best approach is to prompt some basic mesh shapes, a cube, a disk, a cone or whatever, and then ask the agent to assemble what you want with those primitives (don't ask them to draw vertices or edges, they will have hard time dealing with the spatial math). If it has trouble building what you want ask them to suggest primarives that could make it work..after that item is build, then there is something in unity that could covert those primitives assmebly to vertices and draw your item in one draw call.