Gas for agents, cross-chain: pay USDC on Base with a gasless x402 payment (works with 0 ETH anywhere) and receive native gas on Base, Arbitrum, Optimism (ETH) or Polygon (POL) at any address. Price = native value at Chainlink spot +20% +$0.02. Params: to (optional; defaults to the payer), chain (base|arbitrum|optimism|polygon), amount (alias eth) or usd. Max $2/order. Auto-refund in USDC if we can