The biggest challenge an agent will face with tasks like these is the diminishing quality in relation to the size of the input, specifically I find input of above say 10k tokens dramatically reduced quality of generated output.

This specific case worked well, I suspect, since LLMs have a LOT of previous knowledge with HTML, and saw multiple impl and parsing of HTML in the training.

Thus I suspect that in real world attempts of similar projects and any non well domain will fail miserably.