Recommended discovery surface for a public, third-party A2A server

[PortaRegulus]

Hi A2A team — quick question on the right place to surface a public, third-party A2A server.

We (Porta Regulus B.V., operators of https://cvdportal.com) have just shipped an A2A Agent Card at https://cvdportal.com/.well-known/agent-card.json. CVD Portal is a CRA compliance platform — research-coordinated vulnerability disclosure intake and CRA Article 14 / Annex I workflows under Regulation (EU) 2024/2847. The card lists five skills mapped to our public and authenticated MCP tools, uses the MCP custom binding per spec §4.4.6, and advertises streaming + pushNotifications.

Before I go further, I want to make sure I'm aiming at the right surface. I've read:

• docs/topics/agent-discovery.md — the spec explicitly notes no standard registry API exists (§2 Curated Registries, "The current A2A specification does not prescribe a standard API for curated registries.")
• docs/partners.md — appears to list corporate A2A partners only
• docs/community.md — Featured Contributions section lists PRs (sample implementations, tutorials), not live agents. Integrations lists frameworks. SDKs lists language SDKs. No section for live, third-party A2A servers.
• Cloudflare Agents and Google Vertex AI Agent Engine — both are hosting platforms, neither runs a public cross-vendor agent catalog.

Concrete question: is there a recommended surface for a public, non-partner, third-party A2A server to be discovered today, beyond the well-known URI? For example:

1. A "Live Agents" or "Public Agents" subsection of docs/community.md we can open a PR against?
2. Issue Add NEX Agent Co. to Partners + Community Spotlight: first live A2A + x402 dual-protocol agent on Base #2197's "Community Spotlight" path, if that evolves into a live-agents section?
3. Just the well-known URI, with cross-references from MCP registries and similar catalogues?

I'm happy to file a clean PR against whichever doc you point me at, modeled on the format from #2197 (NEX Agent) — the relevant facts for ours would be:

• Agent name: CVD Portal Agent
• Provider: Porta Regulus B.V. (KvK 42062307)
• Agent Card: https://cvdportal.com/.well-known/agent-card.json
• MCP endpoints: https://cvdportal.com/api/mcp/public (unauthenticated) and https://cvdportal.com/api/mcp (authenticated)
• Skills (5): find_vendor_portal, submit_vulnerability_to_vendor, track_vulnerability_report, subscribe_to_report, get_compliance_status
• Capabilities: streaming, pushNotifications (extendedAgentCard: false)
• Spec version: A2A v1.0
• Protocol binding: MCP (custom, per §4.4.6)

Thanks for pointing me at the right path.

[ThriveLabsAI]

We hit the same gap building a public agent surface and landed on a pattern that sidesteps the "no standard registry API" problem:

Beacon + signed knock. Two pieces:

1. Beacon — a short, agent-readable page (plain markdown, no JS) listing your "current asks" — what you want other agents to do right now. Ours: https://knock.thrivers.ai/beacon

2. Knock — instead of a shared secret or a curated-registry account, the caller proves identity with its own Ed25519 key: signs a canonical request and POSTs it. Identity is derived from the key, so there's no account to provision, no impersonation, and no human in the loop. POST https://knock.thrivers.ai/knock

The discovery surface is the entry point — any agent that lands on the beacon can act immediately, no registry approval, no token handout. For agent discovery, a signed "asks + knock" surface closes the loop better than a curated list. Happy to share the ~40-line openssl signing scheme if useful.

[chgaowei]

The well-known Agent Card is the right publish step. A curated "live agents" page is useful for humans, but it is not how another agent finds you next week.

What has worked for us: the Card stays the capability advertisement; a stable identifier (DID + Handle) is how a peer names the agent after the listing moves or the host changes. Discovery can stay well-known + optional catalog. Identity should not be "whoever is on the directory today."

https://fandaigithub.pages.dev/agent-network-protocol/AgentNetworkProtocol