The agentic era runs on two complementary protocols. MCP (Model Context Protocol) connects agents to tools and data. A2A (Agent-to-Agent) connects agents to other agents. Understanding the difference — and when to use which — is essential in 2026.
MCP is vertical: agent reaches down to tools and data. A2A is horizontal: agents communicate with peers. A financial analysis agent might use MCP to call apitree’s search_apis for market data, while using A2A to delegate report formatting to a writing agent.
apitree is a MCP-native platform. When an agent (from any framework — LangGraph, CrewAI, AutoGen) needs external data, it connects to apitree via MCP. apitree handles the last mile: auth, proxy, cache, billing. The agent doesn’t need to know whether the data comes from OpenAI, a Korean government API, or a free public endpoint.
In a multi-agent A2A system, apitree becomes the shared infrastructure layer. Agent A calls agent B via A2A; agent B calls apitree via MCP for data. Both protocols working together.
Sources: OneReach Protocol Guide, InfoQ A2A+MCP Architecture, freeCodeCamp Multi-Agent Book