In Integrations you have your API key (treat it like a password) and the address to receive notifications (webhooks).
Receiving notifications
We notify you when someone gets the card, adds or redeems. In Zapier, create a Zap with Webhooks by Zapier β Catch Hook and paste its address in βNotifications to other appsβ.
Adding from another app
A sale in your till (Square, Holded, Odooβ¦) can add automatically: Webhooks by Zapier β POST to /sumar with the header Authorization: Bearer + your key and the customerβs email or mobile.
The full reference is on the developers page.