You issue an HPN code for each payment. The customer pays your MoMo number using that code as the reference. When the payment lands, Harpoon verifies it and fires your webhook.

Endpoints

Method	Endpoint	Description
POST	/v1/transactions/initialize	Create a payment request
GET	/v1/transactions	List transactions
GET	/v1/transactions/{reference}	Get by reference
GET	/v1/transactions/by-hpn/{hpn_code}	Get by HPN code
GET	/v1/transactions/by-client-ref/{client_ref}	Get by your reference
POST	/v1/transactions/{reference}/reconcile	Manual reconcile by transaction ID
POST	/v1/transactions/{reference}/cancel	Cancel a payment request
GET	/v1/merchant/payment-methods	List your MoMo numbers

Statuses

Status	Meaning
CREATED	Request initialized
PENDING	Awaiting payment
PROCESSING	Payment detected, verifying
SUCCESS	Verified, exact amount
PARTIAL	Verified, customer underpaid
OVERPAID	Verified, customer overpaid
EXPIRED	No payment received before expiry
FAILED	Verification failed
MANUAL_REVIEW	Held for manual review
REFUNDED	Refunded to customer
CANCELLED	Cancelled

SUCCESS, PARTIAL, and OVERPAID all fire a transaction.completed webhook. Read data.status and data.difference to disambiguate.