A2A protocol, agent discovery

Linux Foundationwork-itemcore entry

Verified 2026-10-13. Status as of 2026-10-13. All entries.

Seams: S1

Status

A2A registers /.well-known/agent-card.json for a single AgentCard; proposals for hosts serving several agents (PR #2240, issues #2276 and #2248) were open on 2026-10-13: PR #2240 and issue #2248 have no comment, and issue #2276 has no comment after 2026-10-02.

Relevance

PR #2240 proposes /.well-known/ai-catalog.json as the "Preferred" discovery mechanism, and issue #2276 proposes /.well-known/agent-card-list.json for providers serving multiple agents. The documentation (docs/topics/agent-discovery.md on main) says "The current A2A specification does not prescribe a standard API for curated registries."; AI Catalog and Agentic Resource Discovery (ARD) not found in that file (2026-10-03). darrelmiller wrote on issue #1807 (2026-05-12) "Rather than layering trust information into the AgentCard, we are attempting to use AI Catalog to contain that kind of trust information." HTTP Archive custom-metrics PR #176, merged on 2026-10-07, adds a metric for "/.well-known/agent-card.json" to track its presence and key metadata.

Committed next

None declared in the sources read.

Boundary

A maintainer wrote on PR #418 that the A2A working group "will not be building any kind of registry standard".

Author participation

The author of this map took part in issue #2276 (two comments, 2026-10-02); see Disclosure.

Sources

• https://github.com/a2aproject/A2A/pull/2240 participant or third party, read 2026-10-02 · archived
• https://github.com/a2aproject/A2A/pull/418 maintainer or chair statement, read 2026-10-03 · archived
• https://github.com/a2aproject/A2A/issues/1807 maintainer or chair statement, read 2026-10-03 · archived
• https://github.com/a2aproject/A2A/blob/main/docs/topics/agent-discovery.md normative text, read 2026-10-13 · archived
• https://github.com/HTTPArchive/custom-metrics/pull/176 official decision or commitment, read 2026-10-08 · archived
• https://www.linuxfoundation.org/press/linux-foundation-launches-the-agent2agent-protocol-project-to-enable-secure-intelligent-communication-between-ai-agents official decision or commitment, read 2026-10-03 · archived

Overlaps

Agentic Resource Discovery (ARD), AI Catalog (Agent Card Working Group), Agent2Agent (A2A) protocol, core specification

Neighbours in the map

Solid lines: overlaps declared by one of the two entries. Dashed lines, coloured by seam: entries named by the same seam (S1 to S4) in the seams note. Every node is a link.

Evidence and coverage

Read

Repository items read (updated 2026-01-01 to 2026-10-02): discovery threads in full, the rest by keyword search; docs/roadmap.md and agent-discovery.md on main, 2026-10-03.

Not read

Technical Steering Committee (TSC) minutes and recordings, the diff of PR #2240, the Discord, long identity threads, replies on #2276 after 2026-10-02 (none found: the thread has three comments, the last of 2026-10-02).

Not found

On 2026-10-13 (main at commit 7c861a5): the state, comment count and last update of PR #2240 and issues #2276 and #2248, the latest release (v1.0.1, 2026-05-28), docs/topics/agent-discovery.md (the quoted sentence present; AI Catalog not found in it) and the history of GOVERNANCE.md (last change 2026-08-25). Not found in roadmap.md: discovery.

Open proposals