The email infrastructure
for autonomous invoice processing.
Developers building invoice agents need primitives to receive invoices by email, extract line items, and manage approval workflows via threaded replies. Mailgent provides the email API so your agent can process invoices from receipt to approval without manual data entry.
API Primitives used
mail.list_messagesDetect incoming invoices
Monitor the AP inbox for new invoices. Filter by sender, subject patterns, or attachment type.
mail.get_threadExtract invoice data
Load the full message and attachment to parse vendor name, line items, amounts, and payment terms.
mail.replyRequest corrections
Reply to vendors when invoices have errors — missing PO numbers, incorrect amounts, or incomplete details.
mail.update_labelsTrack approval status
Label invoices as received, approved, disputed, or paid. Maintain a clear processing pipeline.
Invoices arrive by email. Data entry should not be someone's full-time job.
Accounts payable teams receive dozens of invoices daily via email. Each one needs to be opened, amounts extracted, PO numbers matched, approvals routed, and data entered into the ERP. One person doing this manually is a bottleneck that delays payments and frustrates vendors.
Developers building invoice agents need email primitives to receive invoices, read their contents, reply with questions, and track status. Mailgent provides mail.list_messages for intake, mail.get_thread for extraction, mail.reply for vendor communication, and mail.update_labels for pipeline tracking.
How to build it.
mail.list_messagesReceive and parse invoices
Your agent monitors the AP inbox with mail.list_messages, detecting new invoice emails. It retrieves each message with mail.get_thread and extracts vendor, amount, line items, and due date.
mail.get_threadValidate and match
The agent validates extracted data against purchase orders and contracts. If something does not match — wrong amount, missing PO — it flags the invoice for review.
mail.replyRoute for approval or reply
Valid invoices are labeled as approved using mail.update_labels. Invoices with discrepancies get a reply to the vendor via mail.reply requesting corrections.
Example prompt
“Check the AP inbox for new invoices. Extract vendor name and amount from each. Match against open POs. Approve anything under $5,000 that matches, and reply to vendors for any that don't with the specific discrepancy.”
What developers build.
Three-way matching
Build agents that match invoice amounts against purchase orders and receiving reports, approving automatically when all three align.
Early payment discounts
Build agents that detect invoices with early payment terms, prioritize them for approval, and alert finance to capture the discount.
Duplicate detection
Build agents that compare incoming invoices against previously processed ones, flagging potential duplicates before payment.
Vendor reconciliation
Build agents that send monthly reconciliation emails to vendors, comparing your records against their statements.
Why not use AP automation software?
AP automation tools require vendors to submit invoices through a portal or use a specific format. In practice, vendors send invoices however they want — PDF attachments, inline amounts, varied layouts. Your tooling needs to handle email as it actually arrives.
Mailgent gives you the email primitives to work with invoices as they come. mail.list_messages receives them, mail.get_thread reads them, mail.reply communicates with vendors. Your agent handles the variety, not a rigid template.
Isolated AP inbox
Invoice processing happens in a dedicated agent identity. Financial data stays separated from other communications.
Approval audit trail
Every invoice received, approved, or disputed is logged. Clear documentation for financial audits.
Fraud detection ready
Your agent can compare sender addresses, bank details, and amounts against known patterns to flag suspicious invoices.