Can the agents use debit cards?
Stablecoins doesn't make sense here and prefer not to use crypto at all.
Debit cards have to pay too many people. The acquiring bank, the receiving bank, the network, all take their fees. Stripe and their minimum $.30 per transactions leave no room for $0.01 API calls.
Actually, x402 was created because using a credit card programmatically is very difficult.
The whole business of Stripe is based on that: it's so hard for developers to do, and so many regulations, that they would rather pay an another company to do so.
Crypto can be sent just using a contract.transfer() call