Pre-flight a Base payment destination before you send. Verifies the EIP-55 checksum, measures distance from an address you expect — catching a mistyped digit and the shared prefix-and-suffix shape of a ground look-alike — flags the zero address, burn sinks and precompiles, refuses a token offered as its own payee, and reports whether the destination can receive the asset. Returns unknown rather than guessing when bytecode does not decide it. Not a judgement of the counterparty.