Cisco Systems Cisco Systems Protocols for communication between autonomous software agents typically discover agents through documents retrieved over HTTPS from a well-known URI. This model requires a discovering party to already know an agent's host name or URL, or to consult a centralized catalog. It provides no zero-configuration mechanism for enumerating agents that are present on a local network. This document describes how existing, widely deployed protocols, Multicast DNS (mDNS) and DNS-Based Service Discovery (DNS-SD), can be used to advertise and discover agents on a local link, with no new protocol machinery. It presents a general, protocol-independent two- stage discovery model in which lightweight enumeration over DNS-SD is followed by retrieval of full agent metadata over the agent's native transport. It gives a worked instantiation of that model for the Agent2Agent (A2A) protocol, as an example.