---
showArticleList: false
title: Protocols
created: 2026-09-24
visible: true
status: in progress
tags: [agents, protocols]
readability: 3
---

The open standards that let agents, editors, tools, and frontends interoperate, stacking from wire transport up to interface events.

- [A2A](a2a/index.md) - Google's open protocol for independent agents to interoperate, now under the Linux Foundation.
- [ACP](acp/index.md) - Zed's protocol standardizing how editors talk to coding agents.
- [AG-UI](ag-ui/index.md) - 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](agent-host-protocol/index.md) - 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](agents-md/index.md) - the open convention for repo-level agent instruction files.
- [MCP](mcp/index.md) - the open protocol standardizing how AI applications connect to tools and data.

Its members are compared on shared rows in the [Protocols Feature Matrix](protocols-feature-matrix/index.md).

## 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.