Agent Identity and Discovery vs Agent2Agent Protocol
The map lists them as complementary: sites and agents commonly implement both. They answer different questions: Agent Identity and Discovery is a step 1 (Discover) standard, Agent2Agent Protocol step 6 (Coordinate), so they are not substitutes.
| Agent Identity and Discovery AID | Agent2Agent Protocol A2A | |
|---|---|---|
| Lifecycle step | 1 Discover: What is here, and where? | 6 Coordinate: Talk to another agent |
| Answers | Given a domain, where is the agent and which protocol should I speak, with cryptographic proof the endpoint controls the matching key? | How do two independent agents, built on different frameworks, discover each other and delegate a task to completion? |
| Governed by | Agent Community open-source project; editor listed as 'Agent Community'; no formal standards body, though the spec discusses composing with IETF-track work (RFC 9421, RFC 7638, RFC 9728, RFC 8414) | Linux Foundation; Technical Steering Committee with AWS, Cisco, Google, IBM Research, Microsoft, Salesforce, SAP, ServiceNow |
| Status (issuer's words) | Current normative specification | Stable, v1.0.0 |
| Phase | living | stable |
| Version | v2.1.0 (aid2 wire format; aid1 legacy) (2026-06-01) | 1.0.1 (2026-05-28) |
| Form / transport | DNS record | endpoint |
| Found at | _agent.<domain> (DNS TXT); /.well-known/agent (HTTP fallback) | /.well-known/agent-card.json |
| Adoption | observed | claimed — Linux Foundation |
| Evidence | 3 verified | 4 verified, 1 reported |
| Primary use case | Let agents discover my API or service | Let agents talk to other agents |
| Last verified | 2026-10-19 (current) | 2026-10-19 (current) |
| Specification | https://raw.githubusercontent.com/agentcommunity/agent-identity-discovery/main/packages/docs/specification.md | https://a2a-protocol.org/latest/specification/ |
When to use which
- Choose Agent Identity and Discovery when your question is “Given a domain, where is the agent and which protocol should I speak, with cryptographic proof the endpoint controls the matching key?” and you accept its maturity: phase living, adoption observed.
- Choose Agent2Agent Protocol when your question is “How do two independent agents, built on different frameworks, discover each other and delegate a task to completion?” and you accept its maturity: phase stable, adoption claimed (Linux Foundation).
Read the full articles
- Agent Identity and Discovery: Given a domain, where is the agent and which protocol should I speak, with cryptographic proof the endpoint controls the matching key?
- Agent2Agent Protocol: How do two independent agents, built on different frameworks, discover each other and delegate a task to completion?