Given a transaction hash and chain, returns a decoded breakdown: sender, recipient, ETH value transferred, gas used, transaction fee, decoded method name (transfer/approve/swap/deposit/etc.), ERC-20 token transfer details if applicable, block number, block timestamp, and a one-sentence agent-readable summary. Supports Ethereum (default), Base, Polygon, and Arbitrum mainnet. Uses free public JSON-RPC nodes — no API key required, results in ~1-2s.