Is your feature request related to a problem? Please describe.

Currently, the specification assumes that each agent is served from a single base URL, effectively mapping one agent per host. However, in practice, it is common for a single host to act as a routing layer for multiple agents, each accessible via different paths under the same base URL. This setup creates the need for a standardized (open) discovery mechanism that allows clients to enumerate and resolve multiple agents served from a common origin.

Describe the solution you'd like

I propose supporting the discovery of multiple agents under a shared base URL by leveraging the API Catalog format. Specifically, a host could expose an API Catalog that lists multiple agent entries using Linkset objects. Each entry could contain:

• An anchor (optional): The base path for an individual agent (e.g., https://example.org/a2a/v1/agent1), if applicable.
• Link relations to the agent's description: Typical examples include describedby, service-desc, or service-meta. Implementations may also use a URI pointing to the relevant section of the Agent Card specification (e.g., https://a2a-protocol.org/latest/specification/#5-agent-discovery-the-agent-card) as the link relation.

This approach would allow clients to dynamically discover and integrate with multiple agents hosted under a single origin, in a standardized and interoperable way.

For example, if example.org is hosting agent1 and agent2, the expected https://example.org/.well-known/api-catalog would look like the following:

{
  "linkset": [
    {
      "anchor": "https://example.org/a2a/v1/agent1",
      "describedby": [
        {
          "href": "https://example.org/a2a/v1/agent1/agent-card.json",
          "type": "application/json",
          "title": "Agent Card for Agent 1"
        }
      ]
    },
    {
      "anchor": "https://example.org/a2a/v1/agent2",
      "https://a2a-protocol.org/latest/specification/#5-agent-discovery-the-agent-card": [
        {
          "href": "https://example.org/agents/a2a/v1/agent2/agent-card.json",
          "type": "application/json",
          "title": "Agent Card for Agent 2"
        }
      ]
    }
  ]
}

Describe alternatives you've considered

An alternative approach discussed in the GitHub Discussion involves using a custom schema to define and expose agent API endpoint information.

Additional context

• GitHub Discussion
• GitHub Issue on a2a-python
• RFC 9727 api-catalog: A Well-Known URI and Link Relation to Help Discovery of APIs
• RFC 9264 Linkset: Media Types and a Link Relation Type for Link Sets

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