Resolve ENS in either direction on Ethereum: an ENS name (vitalik.eth) → its 0x address, or a 0x address → its primary ENS name (plus avatar when set). The identity read wallet, payment, and UX agents make to verify who they're sending to or to show a human-readable name instead of a raw hex address. Free upstream (Blockscout ENS / live registry); one paid call instead of running your own resolver.