Unlike other payout endpoints in the ZBD API, sending payments to ZBD Gamertags is a synchronous action -> this is why there is no callbackUrl property. The payment either succeeds or fails on the spot.
Important: ZBD Gamertags are mutable and can be changed by users at any time. If you’re implementing user-specific limits (e.g., 1 withdrawal per day) or tracking balances, do not use Gamertags as identifiers. Instead, use the Get ID by ZBD Gamertag endpoint to retrieve the immutable User ID for each Gamertag, then track limits and balances using that User ID. Otherwise, users can bypass your limits simply by changing their Gamertag.