MCP vs. A2A: Comparing AI Agent Communication Protocols (2026)
MCP connects agents to tools and data. A2A connects agents to other agents. Learn the difference, how each protocol works, and when to use both in your stack.
Frequently Asked Questions
What is the difference between MCP and A2A?
MCP (Model Context Protocol) connects an AI agent vertically to tools, data sources, and APIs — giving it things to act on. A2A (Agent2Agent Protocol) connects agents horizontally to other autonomous agents — giving them a way to delegate, collaborate, and hand off tasks. They solve different problems and are designed to be used together.
Who created MCP and A2A?
MCP was created by Anthropic and released as an open standard in November 2024. A2A was created by Google and released in April 2025; Google later donated it to the Linux Foundation in June 2025. Both protocols are vendor-neutral and open source.
Can MCP and A2A be used together?
Yes — they are complementary, not competing. A typical production multi-agent system uses MCP for each agent's tool access (databases, APIs, file systems) and A2A for coordination between agents (task delegation, handoffs, parallel workflows). Think of MCP as giving agents hands, and A2A as giving them a voice.
What is an Agent Card in A2A?
An Agent Card is a JSON file served at /.well-known/agent.json on an A2A server. It acts like a capability resume — describing what the agent can do, what input/output formats it accepts, and how to reach it. Other agents discover a remote agent's capabilities by fetching its Agent Card before sending a task.
Does A2A replace MCP?
No. A2A does not replace MCP — it extends what MCP cannot do. MCP handles the relationship between one agent and its tools. A2A handles the relationship between multiple autonomous agents. The two protocols operate at different layers of the agent stack.