Explainer
How do agents pay for APIs?
Discover, read schema and price, receive 402, pay, retry, verify. No account required if the rail is designed that way.
The clean machine path is: find the resource, read its schema and price, call it, handle HTTP 402, pay through a compatible wallet or token, retry, verify the result against the schema.
x402 exact payments on Base USDC are one implementation. MPP adds cards and Stripe settlement. Visa Intelligent Commerce adds issuer-token agent cards for consumer checkout, which is a different job than paying a JSON API.
If a seller requires a human account, credit card form, or email before the first byte of schema, it is not yet a machine-native API.