MCP vs A2A vs ACP: Open Protocols for Multi-Agent Systems, Compared
MCP vs A2A vs ACP: Open Protocols for Multi-Agent Systems, Compared If you're building a multi-agent system, you've hit this question: how should agents talk to tools, and how should they talk to each other? Wire everything by hand and every new agent adds another custom integration. Pick the wrong protocol and you may rewrite your architecture in six months. This article compares the main open…
Multi-agent systems require open protocols to enable agents to communicate effectively with tools and other agents. If developers manually integrate each agent with every tool, the number of custom integrations rapidly increases with the number of agents and tools. Choosing the wrong communication protocol can lead to significant architectural changes over time.
The article compares the main open protocols for multi-agent systems: MCP, A2A, ACP, ANP, and AG-UI. It begins with a comparison between MCP and A2A, before covering the alternatives. No single protocol can solve all layers of communication in a multi-agent system. By the end, readers will understand what each protocol does, where they overlap, where they differ, and which combination is best suited for their specific stack.
Key points:
- Multi-agent systems need open protocols to avoid custom integrations for each agent-tool pairing.
- Open protocols reduce the number of integrations from N×M to N+M.
- MCP and A2A solve different layers of communication: Agent ↔ Tool/Data and Agent ↔ Agent respectively.
- MCP is maintained by Anthropic and standardized through an open protocol, while A2A is maintained by Google and has gained industry support.
- Each protocol has its own strengths, weaknesses, and suitable use cases.
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