"2026年8月，AI Agent 协议战尘埃落定。MCP、A2A、Agent Plugins 三层分化已成定局。本文拆解三层架构的边界、意义，以及开发者下一步真正的机会在哪里。"
Agent 协议栈三层分化：MCP 管工具、A2A 管协作、Agent Plugins 管分发
2026年8月，协议战结束了。
这不是说竞争消失了——而是战场发生了转移。半年前，开发者还在热烈争论"MCP vs 其它协议哪个更好"，而现在答案已经清晰得让人有点意外：没有哪个更好，只有哪个更适合哪一层。
三层架构是如何成形的
先说背景。AI Agent 的协议演进，在过去两年里经历了一个典型的"分久必合、合久必分"的过程：
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