x402 — HTTP 402 on-chain payments

Coinbase's HTTP 402 payment protocol for paying for web resources with on-chain stablecoins.

Coinbase's HTTP 402 payment protocol for paying for web resources with on-chain stablecoins. Servers return 402 with payment requirements; the agent pays via a facilitator and retries with proof. Agents declare wallet, supported chains (Base, Polygon, Solana), supported tokens (USDC default), and the facilitator URL.

HTTP 402 challenge-response payment protocol — useful for crypto-native agent flows with AstraSync verification.

You declare: wallet address, supported chains, supported tokens, facilitator URL, spending limit.

PDLSS pre-fill: spending limit flows to autonomous and hard limits; facilitator domain to counterparties; currency defaults to USDC if it appears in the supported-token list.

{
  "protocols": ["a2a", "x402"],
  "x402": {
    "walletAddress": "0x1234...",
    "supportedChains": ["base", "polygon"],
    "supportedTokens": ["USDC", "USDT"],
    "facilitatorUrl": "https://pay.coinbase.com",
    "spendingLimit": 100
  }
}