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An invoice intake agent for a growth startup

An agent, now implemented, that reads invoice emails straight from Gmail, matches each one to its purchase order and production batch, and shows how cost per can would change — with a person approving everything before it touches the books.

The Problem

Cost per can is only as accurate as the manual work behind it

Order placement, logistics tracking, and invoice entry into the Excel tolling logs were all manual — and those logs drive the batch-level cost-per-can figure. With the operations analyst role no longer on the team, keeping them current competed with everything else. Every co-packer, ingredient, and freight invoice meant opening the email, reading the PDF, finding the PO, working out which batch it belonged to, and keying it in.

What slips through by hand
  • An invoice whose total doesn't match its own line items
  • A duplicate "reminder" copy of an invoice already paid
  • A freight bill with no PO attached
What we built
  1. Reads invoices directly from the inbox — vendor, line items, and totals pulled from each PDF.
  2. Matches each invoice to the right PO and batch and shows how that batch's cost per can would change.
  3. Flags anything unusual in plain language and waits for a person to approve before anything is written.
How It Works

The AI reads. Fixed rules check. A person decides.

This is where applying AI pays off — and where it deliberately stops. The AI never does the math, and it never changes the books.

01

Read

AI. An AI model reads each invoice PDF and writes down what it says: vendor, line items, totals, PO reference.

02

Match

Fixed rules. Deterministic logic matches the invoice to a PO and production batch, and recalculates cost per can.

03

Flag

Fixed rules. Mismatched totals, duplicates, missing POs, and credit memos are flagged with a plain explanation.

04

Approve

A person. Clean invoices are approved in one click per batch. Flagged ones get an individual decision, logged with who and when.

How We Tested It

Built to break, then run on a real inbox

Most of the test invoices contained a deliberate problem, because real invoices do.

Test 1

12 realistic test invoices

Each one built to trip the logic, checked against an answer key. The matching handled all 12 as required.

  • A wrong printed total
  • A missing PO and an item-code typo
  • A duplicate and a scanned image
  • A credit memo and one invoice covering two batches
  • A statement that isn't an invoice at all
Test 2

Live emails through a real Gmail inbox

Demo invoice emails with PDFs attached, read straight from the inbox with no uploading step.

  • Confirmed the PDFs come through intact and readable
  • Caught a problem we hadn't planted: an email whose subject named one invoice but carried a different one
  • The agent trusted the invoice itself over the email subject
Built Twice

Built twice, then implemented

We built this agent on two different AI models to see what each did well. The differences shaped the design we took into implementation.

Prototype A · Claude

Focused and tested

Intake, matching, and approval, verified end to end.

  • Reads invoice PDFs straight from the inbox
  • Matches to PO and batch with fixed rules, and flags anomalies
  • Checked against 12 deliberately flawed invoices and live emails
  • Approval step records who decided and when
Prototype B · Gemini

Broader scope, not yet proven

Built as a standing agent that takes on more of the analyst's workload.

  • Monitors email and a shared folder continuously
  • Stages entries and drafts a batch summary for one-click approval
  • Drafts routine purchase orders and a weekly logistics status
  • Parallel-run comparison view and Excel export of the tolling log
  • Live inbox connection still being set up; its dashboard figures are sample data, not measured results
Where We Landed

One agent, the best of both

Prototype A's tested extraction, matching, and flagging, with Prototype B's continuous monitoring, drafted POs, weekly status, and parallel-run scorecard layered on.

Time Saved · Estimate

Roughly 10 hours a month back

An illustrative estimate, not a measured result. It assumes about 60 invoices a month, ~12 minutes each by hand versus ~2 minutes to review one. The real figure depends on the client's actual volume.

By hand
~12 hrs / month

Open the email, read the PDF, find the PO, match the batch, key it into the cost log.

With the agent
~2 hrs / month

Review what the agent read and matched, approve the clean ones, decide on the flagged ones.

Beyond hours: reconciliation errors get caught before they reach the books rather than after.

What We'd Measure

Four numbers that prove it works

These are the measures we track to confirm it's working. Results get reported once they're measured on real volume.

Time to log

How long it takes from an invoice, PO, or shipping document arriving to a validated entry in the tolling log. Cost per can is only useful if it's known soon after a run, not weeks later.

Batch cost accuracy

The gap between projected and actual cost per can, and how many post-run invoice surprises show up. This is where silent margin leakage hides.

Straight-through rate & accuracy

The share of documents logged without a human correction, and accuracy on the critical fields: quantities, line-item pricing, batch numbers, freight surcharges. Anything uncertain goes to a person.

Hours reclaimed vs. cost to run

Manual hours saved, net of what it costs to run the agent per invoice. The figure that shows whether it pays for itself.

Next Step

Now implemented

The agent is now implemented for the client, with a person approving before anything is written to the books. We scoped the build at 4–6 weeks, with messy, inconsistent invoice formats as the main risk. The time-saved figures above stay estimates until we measure them on real volume.

The pattern is the point: find the manual, error-prone work, put AI only where reading and judgment are needed, keep rules and people in charge of the rest.

Where could an agent like this pay off for you?

Book a free scoping call — a short conversation about your current systems and where the team feels the most pain, manual work, or lag.

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