My accountant asked for 'a little tool.' Replit built it. Zapier connected it. She uses both halves

The request sounded like a Zapier job: bank CSV exports in, monthly summary out. But the summary needed real logic — category rules she keeps changing, a running total by quarter, a PDF she could send to her tax person. I started with Zapier and got four zaps, two formatter steps, and a Google Sheet that collapsed under its own conditional formatting. Not great.

Replit's agent built the actual thing in one afternoon: a tiny web app where she uploads the CSV, the rules live in a config she can (with effort) edit, and the summary renders as a clean page with a print button. Was the code elegant? No. Did it work? On the third try, and the first two failures were my vague prompts, not the tool.

Then the part Replit couldn't do: getting the file in without her opening anything. She wanted the CSV emailed, processed, and the summary back, automatically. That's Zapier's whole personality — it catches the email, hits the app's upload endpoint, and mails the result. The app and the pipe needed each other.

Costs ran as expected: Zapier's task pricing is fine at this volume, and Replit's agent hours got consumed fastest when I was imprecise. Lesson from the bill: know what you're asking for before you let an agent build it.

The boundary I'd draw now: if your 'little tool' is really a workflow between existing apps, Zapier alone. If it's actual logic with an interface, Replit builds it and Zapier feeds it. The mistake is asking either to do the other's half — I did, twice, and the accountant's PDF is what taught me.