Get the right spreadsheet formula every time

Describe the sheet, not just the goal

Most bad formulas come from the AI guessing your layout. Tell it the app, the sheet names, the columns and a couple of sample rows.

Google Sheets. Sheet "Orders": A=Order ID, B=Date, C=Customer, D=Amount (£).
Sheet "Customers": A=Customer, B=Region.
In Orders!E2 I want the customer's Region, looked up from Customers.
Then in a summary sheet, total Amount by Region for 2026 only.
Give me the formulas and explain each in one line.

Check before you trust

1. 1Test on 3 rows you can work out by hand.
2. 2Ask: "What edge cases would break this formula?" (blanks, text in number columns, duplicates)
3. 3Ask for an IFERROR-wrapped version if missing data is normal.