How AI agents pay with stablecoins over x402

An AI agent pays an x402 API with a stablecoin by answering HTTP 402.

The server returns payment terms that name an asset, often USDC, plus a network, an amount, and a recipient.

The agent signs that transfer and retries the request with proof of payment.

1.What the caller signs

The payment terms travel with the 402. For the common scheme the caller signs an authorization, and a facilitator submits it on chain. vet402 records the asset it paid on each purchase.

The pinned asset is USDC on Base, Solana, Arc, Celo, Stellar, and Arbitrum One. Tempo uses USDC.e over MPP (Machine Payments Protocol). XRPL uses RLUSD. BNB Chain uses USD1.

2.What vet402 measures

vet402 sends an unpaid request, reads the 402, and buys when the scheme, the network, the asset, and the price match the catalog. A longer note on the protocol is What is x402. How to read a seller before paying is on its own page.

Live counts are the chain pages and /api/v1/observatory/state. Purchase lanes with a page: Base, Solana, Tempo, XRPL, Arc, Celo, Stellar, Arbitrum One, BNB Chain.