How to build
How to build an invoice and document processing agent
Document processing is the most reliably awful job in any back office: open the PDF, find six numbers, type them somewhere else, repeat. It is also unusually well suited to being automated, because the output is structured and checkable — you can tell immediately whether the total was read correctly, which is not true of most things an agent produces.
What you’re building
A document processing agent reads invoices, receipts, contracts or forms — including scans and photographs — pulls out the fields you specify, validates them against rules you set, and writes the result into a spreadsheet, a database or your accounting tool.
Who this is a good fit for
- Finance teams keying invoices by hand into a sheet or accounting system
- Anyone reconciling receipts at month end
- Ops teams processing forms that arrive as PDFs or photos
How to build it
Step 1
Say which fields matter and what must be true of them
List the fields, then the validation. The validation is the half people skip and the half that makes it usable — "line items must sum to the total" and "flag anything over ₹50,000" are what turn extraction into something you can act on without re-checking every row.
Invoice Agentinvoice-agentDescribe it
Build an invoice processing agent. For every invoice emailed to accounts@, extract vendor, invoice number, date, line items, tax and total. Validate that line items plus tax equal the total, and flag any invoice over ₹50,000 or from a vendor we haven't paid before. Write everything to our Sheet and post flagged ones to #finance.Build itStep 2
Connect the inbox and the destination
Invoices usually arrive by email, so Gmail or Outlook is the trigger. The destination is wherever your books actually live — a Sheet for most teams, QuickBooks if you are past that. Drive or Dropbox can be connected too, for the ones that arrive as shared folders.
Invoice Agentinvoice-agentConnect
Gmailread accounts@ attachmentsConnectedGoogle Sheetsappend rowsConnectedQuickBookscreate billsConnectedSlackpost to #financeConnectedStep 3
It builds extraction, validation and the exception path
It sets up the parsing for each document type, the validation rules, and — most importantly — what happens when something fails. The exception path is the design decision that matters: a document that cannot be read confidently should land in a review queue, never be written with a guessed total.
Invoice AgentTrigger: attachment to accounts@Extract: vendor, number, date, line items, tax, totalValidate: line items + tax = totalFlag: > ₹50,000 or new vendor → #financeLow confidence → review queue, not writtenStep 4
Review the flagged ones, let the rest flow
In practice most invoices pass cleanly and a small tail needs eyes — a bad scan, an unusual layout, a new vendor. That tail is the point of the review queue. The measure of success is not a hundred per cent automation; it is that you only look at the ones worth looking at.
invoices.trysomething.siteVendor Invoice Date Total Status Northwind Supplies INV-4821 2 Oct ₹18,400 Posted Kestrel Print KP-0917 3 Oct ₹64,200 Flagged — over limit Atlas Freight — 4 Oct — Review — poor scan
What it does once it’s running
- Reads PDFs, scans and photographs, not just clean digital documents
- Extracts exactly the fields you name, including line-item tables
- Validates arithmetic and flags anything breaking your rules
- A review queue for low-confidence documents instead of a guessed value
- Writes to Sheets, QuickBooks or a database, with the original attached
Tools it connects to
What it won’t do
- Genuinely poor scans — skewed, low-resolution, handwritten — will land in review, which is the correct behaviour rather than a workaround
- Unusual layouts need a few examples before accuracy settles
- Anything with legal or tax consequence should keep a human approval step; the agent is there to remove the typing, not the responsibility
Start from a template instead
Each of these opens with the prompt already written. Edit it before you build.
Common questions
- Does it work with scanned or photographed invoices?
- Yes, including photos taken on a phone. Quality still matters — a badly skewed, low-resolution scan goes to the review queue rather than being guessed at, which is deliberate.
- What if it reads a number wrong?
- The validation rules are there to catch exactly that. If line items do not sum to the total, or a value breaks a threshold you set, it is flagged rather than written. Documents it is not confident about never reach your books unreviewed.
- Can it post straight into our accounting system?
- QuickBooks can be connected directly. Most teams start by writing to a Sheet while they build confidence, then switch the destination once the accuracy is proven — which is a one-sentence change.
- How many documents can it handle?
- Far more than a person, and the volume is rarely the constraint. The practical limit is how much of the tail you want reviewed, which you control through the confidence and validation rules.
Related use case
AI agent for operations & project automationCreate, sweep, and sync tasks across chat, issue trackers, and code automatically.
Build it in the next ten minutes
Start with a sentence. Leave with a working app on its own URL.