The open standards that let agents, editors, tools, and frontends interoperate, stacking from wire transport up to interface events.
- A2A - Google’s open protocol for independent agents to interoperate, now under the Linux Foundation.
- ACP - Zed’s protocol standardizing how editors talk to coding agents.
- AG-UI - CopilotKit’s agent-to-frontend event protocol, 1.0 since September 2026 with 7.5 million monthly npm downloads, the rendering half of the protocol stack.
- Agent Host Protocol - Microsoft’s sessions-server spec with six-language SDKs, VS Code rebuilding its agent infrastructure on it, spec still at v0.9.0.
- AGENTS.md - the open convention for repo-level agent instruction files.
- MCP - the open protocol standardizing how AI applications connect to tools and data.
Its members are compared on shared rows in the Protocols Feature Matrix.
Changes #
- 2026-08-24 - Added A2A.
- 2026-08-24 - Added ACP.
- 2026-08-24 - Added AGENTS.md.
- 2026-08-24 - Added MCP.
- 2026-08-30 - Added Agent Host Protocol.
- 2026-09-16 - Added AG-UI.