I run a small Italian energy tariff comparison site called SwitchAI. For a while the plan was completely ordinary: user uploads a PDF bill, server parses it, site shows cheaper offers. Then I tested that plan against ten real bills from five different Italian providers, and it fell apart in a way that ended up reshaping the whole product.
Here's what happened, and what I think it says about building for a world where the "user" filling in your form is increasingly an LLM holding a PDF, not a person typing numbers.
The parsing problem that wasn't really a parsing problem
Italian energy bills are not a standard format. Enel, Octopus, A2A, NeN, and Eni Plenitude each lay out consumption, POD/PDR codes, and cost breakdowns differently enough that a regex-based parser trained on one provider silently breaks on another.
My hosting made this worse: shared OVH hosting, no pdftotext, no Python runtime, no OCR. I could get a PHP-native parser working reasonably well on Enel bills. Octopus bills, structured completely differently, just didn't cooperate.
