Agent2Agent Protocol (A2A) vs Secure Low-Latency Interactive Messaging (SLIM)
The map lists them as complementary: sites and agents commonly implement both.
| Agent2Agent Protocol A2A | Secure Low-Latency Interactive Messaging SLIM | |
|---|---|---|
| Lifecycle step | 6 Coordinate: Talk to another agent | 6 Coordinate: Talk to another agent |
| Answers | How do two independent agents, built on different frameworks, discover each other and delegate a task to completion? | How can agents send secure, low-latency, group-aware messages (point-to-point, pub/sub, fire-and-forget, streaming) as a transport underneath higher-level protocols like A2A and MCP? |
| Governed by | Linux Foundation (Technical Steering Committee: AWS, Cisco, Google, IBM Research, Microsoft, Salesforce, SAP, ServiceNow); Agentic AI Foundation (AAIF) since 17 August 2026 | Linux Foundation (AGNTCY project); originally donated by Cisco |
| Status (issuer's words) | Stable, v1.0.1 | "Next-generation communication framework that provides the secure, scalable transport layer for AI agent protocols like A2A and MCP" |
| Version | 1.0.1 (2026-05-28) | draft-mpsb-agntcy-slim-02 (2026-07-19) |
| Form / transport | endpoint | endpoint |
| Found at | /.well-known/agent-card.json | none |
| Implementation | multi-implementation — 150+ supporting organizations, claimed by the Linux Foundation on 9 April 2026 (https://www.linuxfoundation.org/press/a2a-protocol-surpasses-150-organizations-lands-in-major-cloud-platforms-and-sees-enterprise-production-use-in-first-year). Card-version censuses are separate measurements, kept with their frames and not averaged. Agenstry 2026-09-01 (https://agenstry.com/blog/state-of-the-agent-card): of 1,910 cards declaring protocolVersion, 65.5% (1,252) are 0.3.x and 25.5% (488) are 1.0.x. Emissar 2026-10-02 (https://emissar.ai/learn/a2a-adoption-2026): 276 cards on the Tranco top 1M (205 in v1.0 shape, 71 in v0.3 shape, 0 signed, 0 in the top 1,000 domains). APIs.io / Kin Lane 2026-09-21 (https://apievangelist.com/2026/09/21/a2a-adoption-is-421-of-27840-and-most-of-them-arrived-with-the-card/): 421 parseable cards out of 4,718 hosts probed (27,840 providers). rStation 2026-10-12 (https://rstation.ai/problems/ai_agent/papers/1): 661 cards on 2,164 x402 seller hosts (189 pass their attributed version and fail a check that assumes 1.0). | shipping |
| Evidence | 11 verified, 2 reported | 4 verified, 1 reported |
| Primary use case | Let agents talk to other agents | Let agents talk to other agents |
| Last verified | 2026-10-23 (current) | 2026-10-23 (current) |
| Specification | https://a2a-protocol.org/latest/specification/ | https://github.com/agntcy/slim |
When to use which
- 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: status "Stable, v1.0.1", implementation multi-implementation (150+ supporting organizations, claimed by the Linux Foundation on 9 April 2026 (https://www.linuxfoundation.org/press/a2a-protocol-surpasses-150-organizations-lands-in-major-cloud-platforms-and-sees-enterprise-production-use-in-first-year). Card-version censuses are separate measurements, kept with their frames and not averaged. Agenstry 2026-09-01 (https://agenstry.com/blog/state-of-the-agent-card): of 1,910 cards declaring protocolVersion, 65.5% (1,252) are 0.3.x and 25.5% (488) are 1.0.x. Emissar 2026-10-02 (https://emissar.ai/learn/a2a-adoption-2026): 276 cards on the Tranco top 1M (205 in v1.0 shape, 71 in v0.3 shape, 0 signed, 0 in the top 1,000 domains). APIs.io / Kin Lane 2026-09-21 (https://apievangelist.com/2026/09/21/a2a-adoption-is-421-of-27840-and-most-of-them-arrived-with-the-card/): 421 parseable cards out of 4,718 hosts probed (27,840 providers). rStation 2026-10-12 (https://rstation.ai/problems/ai_agent/papers/1): 661 cards on 2,164 x402 seller hosts (189 pass their attributed version and fail a check that assumes 1.0).).
- Choose Secure Low-Latency Interactive Messaging when your question is “How can agents send secure, low-latency, group-aware messages (point-to-point, pub/sub, fire-and-forget, streaming) as a transport underneath higher-level protocols like A2A and MCP?” and you accept its maturity: status ""Next-generation communication framework that provides the secure, scalable transport layer for AI agent protocols like A2A and MCP"", implementation shipping.
Read the full articles
- Agent2Agent Protocol: How do two independent agents, built on different frameworks, discover each other and delegate a task to completion?
- Secure Low-Latency Interactive Messaging: How can agents send secure, low-latency, group-aware messages (point-to-point, pub/sub, fire-and-forget, streaming) as a transport underneath higher-level protocols like A2A and MCP?