Why invoices need two extraction shapes, not one
Most PDF-to-table tools assume a single flat grid, which works for a plain data table but breaks on an invoice, where a repeating line-item block sits above or below one-off header fields that only ever appear once. Extract's prompt explicitly separates the two: line items become table rows keyed by description/quantity/unit_price/tax_rate/line_total, while vendor, invoice number, dates, and totals are pulled as document-level fields. The line-item check — line_total against quantity × unit_price, adjusted for where tax is applied — is the same arithmetic an accounts-payable clerk runs manually, done automatically so a transposed digit surfaces as a flagged row rather than an invoice paid for the wrong amount.