Use when you need to confirm or explain a transaction (e.g. verify a payment arrived): fetches the transaction, its receipt and block from Base or Ethereum and returns success/failed/pending, confirmations, timestamp, from, to, native value, gas used and fee, the 4-byte method selector, contract created, and every ERC-20 Transfer log decoded with token symbol and human amount. 404 (not charged) if the hash is unknown. Paid tool: x402 USDC on Base, $0.002 per successful call; call without payment to receive the PaymentRequired object.