Current gas prices and EIP-1559 fee recommendations across 6 major EVM chains: Ethereum, Base, Arbitrum, Optimism, Polygon, BNB Chain. Returns base fee, priority fee percentiles (slow/standard/fast), and estimated ETH/MATIC/BNB cost for a standard 21k-gas transfer. All sourced from free public RPC endpoints — no API key needed. Use before sending on-chain transactions, estimating agent operating costs, or comparing chain fees for routing decisions.