ACP vs MCP
MCP versus the two protocols called ACP, and how they fit together.
MCP lets an AI app use outside tools and data, such as files, databases and search. ACP is not a rival to it: the letters stand for two other protocols with different jobs. Agent Client Protocol connects a code editor to a coding agent, and Agent Communication Protocol connected agents to each other before it joined A2A under the Linux Foundation. Agent Client Protocol is built to work with MCP, because the editor passes your MCP servers on to the agent.
Good for
- Developers who saw ACP in an editor or agent and want to know how it differs from MCP
- Agent builders choosing a protocol for agent-to-agent calls
- Claude Code, Codex and Cursor users wiring up tools
- Anyone puzzled by two protocols sharing three letters
Side by side
Use MCP to give an AI app tools and data. Use Agent Client Protocol to plug a coding agent into an editor.
| Option | MCP | ACP: Agent Client Protocol | ACP: Agent Communication Protocol |
|---|---|---|---|
| Connects | AI app to tools and data | Code editor to coding agent | Agent to agent |
| Typical use | Claude reads your calendar | Editor runs Codex CLI | Agents from different frameworks |
| Talks over | Stdio or HTTP | Stdio, remote in progress | REST API |
| Status | Open standard | v1 latest, v2 draft | Now part of A2A |
| Relation to MCP | Tools and data layer | Reuses MCP types | Has an MCP adapter |
Which to pick
Our advice: use MCP when an AI app needs tools or data. Use Agent Client Protocol when you build or choose an editor and a coding agent. For agent-to-agent calls, look at A2A, which now includes the Agent Communication Protocol.
The main limit: these three protocols solve different problems, so the right pick depends on what you are connecting.
Best for
- MCP: connecting Claude, ChatGPT or Claude Code to apps, files and databases
- Agent Client Protocol: running one coding agent in several editors
- Agent Communication Protocol or A2A: agents from different frameworks calling each other
Skip it if
- MCP: you need an editor to talk to a coding agent, which is Agent Client Protocol's job
- Agent Client Protocol: you want agents to call each other over the network, since remote support is still in progress
Questions
What does ACP stand for?
Two things. Agent Client Protocol links code editors to coding agents. Agent Communication Protocol links agents to each other. Check which one a page means before you compare it to MCP.
What is the difference between ACP and MCP?
MCP connects an AI app to tools and data. Agent Client Protocol connects a code editor to a coding agent. They sit at different points in the same setup and do not replace each other.
Does ACP replace MCP?
No. The Agent Client Protocol reuses MCP's data types where it can, and the editor passes its MCP servers to the agent so the agent can connect to them directly.
Do ACP and MCP work together?
Yes. In an ACP setup, the editor is the client and the agent is the program it starts. The agent still uses MCP servers for tools. The Agent Communication Protocol site also lists an MCP adapter.
What is the Agent Communication Protocol?
It is an open protocol, built with the BeeAI platform as its reference implementation, that lets agents from different frameworks talk over a REST API. Its site now says it is part of A2A under the Linux Foundation, with a migration guide.
What is the Agent Client Protocol used for?
It lets any compatible editor run any compatible coding agent. Its agent list includes Codex CLI and Claude Agent through adapters, Gemini CLI, Goose and Hermes Agent.
ACP vs A2A: which should I use?
A2A is an open standard for agents talking to other agents. The Agent Communication Protocol site says it is now part of A2A, so for agent-to-agent work start with A2A. Agent Client Protocol is for editors and is a separate project.
Is MCP the same as an API?
No. An API is one service's own interface. MCP is a shared standard, described as a USB-C port for AI apps, so an app that speaks MCP can use any MCP server.
Can I use ACP in Claude Code?
ACP editors can run Claude through an adapter: the ACP agent list shows Claude Agent via Zed's SDK adapter. Claude Code itself connects to tools using MCP.
Sources
Docs, issue trackers and discussions this page is built from.
Show all 7Hide
- What is the Model Context Protocol? · modelcontextprotocol.io
- Agent Client Protocol: Introduction · agentclientprotocol.com
- Agent Communication Protocol: Welcome · agentcommunicationprotocol.dev
- Agent Client Protocol: Architecture · agentclientprotocol.com
- MCP architecture · modelcontextprotocol.io
- ACP agents · agentclientprotocol.com
- A2A Protocol · a2a-protocol.org