httppayai

x402-crosschain-gas

Stop opening five explorers to price one transaction: one GET returns what each chain is charging for gas right now — for base, eth, arbitrum, optimism and polygon: the current gas price in gwei (with the raw wei the RPC returned), the latest block's base fee, the priority fee a 50th-percentile transaction actually paid across the last five blocks, the next block's base fee under the EIP-1559 formula, the block number and timestamp those numbers came from, and the public RPC that answered. curl: GET /gas?chains=base,eth (omit chains for all five; aliases like ethereum or arb work). Response: {gas:[{chain,chain_id,gas_price_gwei,base_fee_gwei,priority_fee_gwei,block:{number,timestamp},source_rpc,fetched_at}]}. Every value is a measurement from a public RPC, never an estimate: a chain no RPC answered for is listed in chains_unavailable with the reason, and a figure that could not be measured is null. Values are cached for 15 seconds, and each one carries the fetched_at of the measurement (not of this response). No keys, no account, read-only, one GET, one delivery — 0.001 USDC. A purchase is two calls by design: this first call returns 402 with the price and the payment terms, and you then repeat the same request with the PAYMENT-SIGNATURE header to receive the 200 delivery.