Client and server responsibilities

The merchant server is responsible for the amount, order authorization, and the decision to deliver goods.

Task	Responsible party
Finalizing the order, verifying the owner, calculating the price	Merchant server
Creating the payment with the API key	Merchant server
Saving the order-to-payment ID mapping	Merchant server
Top-level navigation to checkoutUrl	Merchant's browser screen
Confirming the payment details, passkey signature	STBLpay checkout page
Applying for JPYC issuance, approving the issuance reservation, transaction decisions	JPYC EX screen (the buyer deals with JPYC EX directly; STBLpay is not involved)
Webhook verification, status lookup, order update, goods delivery	Merchant server
Showing order status after the buyer returns	Merchant site screen

Do not trust the amount or status sent from the browser. Receive the order ID and calculate the price from the data stored on your own server.

Keep the API key and the Webhook signing secret only on the server. Do not reproduce passkey signing on a merchant page, and do not embed the checkout screen.

Refunds use a different authority and path from receiving payment results. The only path is for the owner to approve with a passkey in the merchant console. Merchant servers cannot call a refund API (none exists). See Scope of refunds.