Automate Invoice Intake Without Sending Anything to the Cloud

Supplier invoices are the most common thing people want to automate and the most common thing they should not hand to a cloud service. They contain your suppliers, your prices, your margins and your payment terms, and they arrive as PDFs that need reading rather than parsing.

This walkthrough builds the smallest honest version: read from a folder, extract fields, verify the arithmetic in a deterministic engine rather than a model, and escalate anything that does not add up. It is deliberately not a system that pays invoices.

The shape

The skill

One SKILL.md, with the rules that matter written as instructions the model cannot talk itself out of. The three constraints at the bottom are the difference between something you can defend to an auditor and something you cannot.

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31---name: "Invoice Intake"slug: "invoice-intake"version: "2026.1"triggers: ["invoice", "supplier", "bill", "racun"]moduleType: "calc"domains: ["admin", "finance"]outputSchema:  type: object  required: [supplier, netMinor, vatMinor, grossMinor, verdict]  properties:    supplier:   { type: string }    invoiceNo:  { type: string }    netMinor:   { type: integer }    vatMinor:   { type: integer }    grossMinor: { type: integer }    verdict:    { type: string, enum: [book, review] }    reason:     { type: string }---Read one supplier invoice from the workspace and return the fields above.Hard rules:- Amounts are integers of the smallest currency unit. Never emit a float.- Do not compute or check any total yourself. Call the calculation tool and  use what it returns, including for the VAT line.- If the arithmetic does not reconcile, if the supplier is unknown, or if any  required field is missing or ambiguous, return verdict: review with a reason.  Never guess a value to make the document balance.

Run one through

Start with dryRun: true. It routes the message and performs the calculation without calling a model at all, which is exactly what you want while you are still checking that the maths is right.

# the file is inside fsRoot; anything outside it is refused$ curl -s -X POST http://127.0.0.1:18790/tools/run \>   -H "Authorization: Bearer $(cat ~/.clerq/gateway-token)" \>   -H "Content-Type: application/json" \>   -d '{"tool":"fs.read","input":{"relativePath":"inbox/2026-09/INV-4471.txt"}}'{"path":"/Users/you/clerq-workspace/inbox/2026-09/INV-4471.txt","bytes":2184,…}$ curl -s -X POST http://127.0.0.1:18790/task \>   -H "Authorization: Bearer $(cat ~/.clerq/gateway-token)" \>   -H "Content-Type: application/json" \>   -d '{"message":"process invoice INV-4471","dryRun":true}'{"dryRun":true,"matchedSkill":"invoice-intake", "calculation":{"netMinor":120000,"vatMinor":30000,  "grossMinor":150000,"engine":"local"}, "llm":{"called":false,"reason":"dryRun"}}# a document that does not reconcile does not get booked$ curl -s -X POST http://127.0.0.1:18790/task -H "Authorization: Bearer $(cat ~/.clerq/gateway-token)" \>   -H "Content-Type: application/json" -d '{"message":"process invoice INV-4472","dryRun":true}'{"verdict":"review","reason":"gross 1512.00 != net 1200.00 + vat 300.00"}

What to keep a person for

• ▸Anything that does not reconcile. No exceptions, no tolerance band that quietly swallows small errors.
• ▸New suppliers. First invoice from anyone is a review, always. This is also the control that catches invoice fraud.
• ▸Payment itself. Extraction and checking can be automated; authorising money leaving the company should not be.
• ▸Anything the model flagged as ambiguous. A skill that never returns "review" is not being honest with you.

If you have not run the agent yet, start with the quickstart. Before you point it at real invoices, read how to secure it — this is the tutorial where it starts touching documents that matter.