Agent protocols have solved a lot of problems — tool integration, inter-agent communication, capability negotiation — but they still assume one thing: that you already know where the other agent lives. A2A and MCP both rely on centralized catalogs or pre-configured HTTPS endpoints. On a developer workstation, an edge site, or a meeting room network where agents appear and disappear dynamically, that assumption breaks down.
Cisco Systems has proposed a solution that avoids inventing anything new. Published July 6, 2026, the Internet-Draft draft-jakab-dawn-agent-discovery-mdns-00 describes how the mDNS and DNS-SD protocols — the same stack that lets your phone discover a nearby printer or AirPlay speaker — can advertise and enumerate agents on a local link.
The design rests on a single protocol-independent service type: _agent._tcp. Any agent that speaks A2A, MCP, or a future protocol registers itself under this same type. The specific protocol is not baked into the service identifier; instead it appears in a proto TXT key. This means a discovering party browses once and sees every local agent, regardless of protocol, then filters by what it actually needs.
Discovery itself happens in two stages. The first is a lightweight DNS-SD browse that returns a minimal descriptor for each agent. The second stage — retrieval of the full agent description, authentication, and session initiation — happens over the agent’s native transport.
The security model is explicit: mDNS and DNS-SD do not authenticate advertisements. Any host on the local link can publish an agent service instance, including one that impersonates another. Trust is established in the second stage, through the transport security and authentication mechanisms of the agent protocol itself.
For builders working on local or edge agent deployments, the practical implication is straightforward: the network already knows how to do this. The mDNS and DNS-SD stack is mature, widely deployed, and handles exactly the zero-configuration problem that agent discovery needs solved at the local level.