x402 Protocol

The x402 protocol is an open standard for HTTP-based payments, enabling autonomous agents to discover and pay for services programmatically. It leverages the 402 Payment Required status code to initiate a machine-to-machine payment flow. You can read more about the original specification in the Coinbase x402 repository.

Deviation Notice

AgentBureau implements x402 with payment_scheme: tx-hash-v1, not EIP-3009. Agents expecting facilitator-submitted authorizations will not work — see the tx-hash-v1 scheme for integration details.

Protocol Headers

The following headers are used to coordinate the payment between the agent and the AgentBureau gateway.

Emitted by Gateway (402 Response)

Header	Description
PAYMENT-REQUIRED	The amount and currency required (e.g., 5.00 USDC).
PAYMENT-LINK	An ethereum: URI or direct wallet address for payment.
X-PAYMENT-NONCE	A unique nonce for the current payment request.
X-PAYMENT-SCHEME	Set to tx-hash-v1 for AgentBureau.

Expected from Agent (Retry Request)

Header	Description
PAYMENT-SIGNATURE	The transaction hash of the USDC transfer (e.g., 0x...).
Idempotency-Key	A unique string to prevent duplicate processing of the same task.