Persi
My finance and day-to-day app, with an AI assistant that logs expenses by voice. It replaced my Excel spreadsheet.
- Role
- Product, design and engineering
- Period
- 2026
- Stack
- Next.js 16 · Convex · Clerk · Claude API · MCP
Demo with sample data, recreated from the product.
01 — The problem
A spreadsheet works until you have to enter every expense by hand.
I tracked my finances in Excel: installments, cards, due dates and promotions that expire. I wanted to say “spent 28k at Coto with the Visa” and have it recorded right, in the right account and without rounding errors.
02 — What I did
Finances, tasks and reminders, with an assistant inside.
- Monthly dashboard compared against the same period last month
- Transactions, accounts, cards with installments and recurring due dates
- Persi AI: logs and answers with tool calling, and shows how it computed each answer
- Excel and CSV importer with duplicate detection and rollback
- An MCP server to use Persi from Claude or ChatGPT, plus push notifications
03 — Key decisions
Claude interprets, Convex computes
The model understands the request and picks typed tools; every amount and total is computed by the server.
Exact money
Amounts in integer cents and Buenos Aires civil dates: an expense on the 31st at 11:30 pm never lands in the next month.
Nothing duplicates
Each operation carries an idempotent id: an assistant retry or a re-import never logs an expense twice.
04 — Outcome
I use it every day.
Persi replaced my spreadsheet: I log expenses by talking, see the month at a glance and check it from Claude when I'm doing something else.