Constant DISCOVER_AGENTS_TOOL 

pub(crate) const DISCOVER_AGENTS_TOOL: &str = r#"{
  "name": "DiscoverAgents",
  "description": "List the agents and instances reachable from here across the muxbus delivery tiers (host, LAN, cloud), so you can pick a valid target before SendMessage. Returns JSON: host.addressable (agents reachable right now via local delivery), host.agents (this host's agent directory, each with an `addressable` flag), lan (LAN peers and the agents on them), and wan.local_agents_subscribed (THIS host's own agents that are subscribed to the cloud relay — not a list of remote agents you can reach over WAN; the relay exposes no such directory, so a cloud-only target simply won't appear anywhere in this output). Addressing is by agent name, case-insensitive. Takes no arguments.",
  "inputSchema": {
    "type": "object",
    "properties": {}
  }
}"#;