We have developed something similar inhouse (a CLI tool for agents that has a few dozen utilities for manipulating KiCad files) and the results are pretty good. In terms of complexity, I would say that tasks like "replicate the layout from the datasheet of this amplifier and make me a testboard" or "look, we need an adapter that goes from <this devkit (insert PDF schematic)> to <these boards (insert KiCad file)>" are basically solved. More dense layouts are a stretch at the moment. (speaking about Opus 5.5 specifically here, other models are likely worse at these visual-coding tasks anyway)

In terms of result quality, I would say that the results are distinctly "2024/2025 LLM programming quality". The models lack a certain... taste? Good and careful prompting can help, but for example "use hierarchical sheets" can yield a single hierarchical sheet containing 3 copies of the same thing instead of three instances of a hierarchical sheet containing the same thing once. When pointed out, the model can of course do it no problem the way you want.