Agent-to-Agent Discovery in SMESH: Why Coordination Isn't Enough Without Runtime Introductions

You can build a working agent mesh with QUIC transport, encrypted messaging, and decentralized coordination. Five processes can reinforce independent conclusions and let unsupported signals decay. The mesh works. Then you try to introduce it to another agent and discover you have no standard way to ask what the swarm can do. No retained task to retrieve after an internal signal expires. No interoperable progress stream. No cancellation contract. No artifact another framework would understand. SMESH is a Rust-based decentralized agent framework that hit this boundary. The author had built a society with no border crossing. The solution was Google's Agent2Agent (A2A) protocol, announced in April 2025 and moved under Linux Foundation governance in June 2025. A2A provides the missing public contract: a way for agents built by different vendors to discover one another, exchange messages, and collaborate without sharing private memory, tools, or internal plans. The Cold-Start Problem in Agent Meshes Traditional service meshes solve discovery with a central registry. Kubernetes has etcd. Consul has its catalog. Envoy has xDS. You register your service, get a DNS name or IP, and other services find you. This works because services are relatively static and the registry is the source of truth. Agent meshes are different. Agents are ephemeral, context-dependent, and often spawned on demand. They need to: Discover peers without a central registry Exchange capability metadata at runtime Negotiate protocols without pre-shared configuration Maintain security boundaries during introduction The coordination primitives (message passing, consensus, signal decay) assume agents already know about each other. Discovery is the layer below coordination. SMESH had the top layer working but no way to bootstrap the bottom layer without manual wiring. What A2A Provides A2A is not a coordination protocol. It is an introduction protocol. The spec defines: Discovery handshake : How agents announ