guard-x402-payments

Guard an autonomous agent's x402 payment with the live IntentFence service before it signs. Use when an agent receives a PAYMENT-REQUIRED challenge, is about to pay an x402 endpoint, needs to enforce a USDC price ceiling or payee allowlist, or needs signed evidence that an exact Base USDC quote was checked. Also use for a free declared-action policy preview when no x402 challenge exists.