MCP vs A2A
MCP connects an agent to tools and data. A2A (Agent2Agent) connects an agent to other agents, so they can discover each other and delegate work across frameworks and vendors.
They are often framed as rivals. The Linux Foundation’s Agentic AI Foundation, which now hosts both, puts them on different layers: MCP “standardizes how agents connect to and interact with tools, data sources, applications, and services,” while A2A “adds an agent to agent interoperability layer.”
A2A joined the foundation as a hosted project on 17 August 2026. Its first stable specification, v1.0, shipped in March 2026 with signed agent cards and version negotiation, and the foundation says it is backed by more than 150 organisations. Backing isn’t the same as production use, so check for deployments in your own stack.
Rule of thumb: tools and data, MCP. Another agent, A2A. Most multi-agent stacks need both.
MCP and A2A compete.
Different layers. Same foundation.
Expose tools and data over MCP. Reach for A2A only when your agent has to delegate to an agent you don’t own.
Don’t pick one protocol for the whole estate. Map which boundaries are agent-to-tool and which are agent-to-agent.
Sources
- AAIF, A2A joins AAIF’s open agentic stack · 17 Aug 2026
- MCP specification 2026-07-28, changelog · 28 Jul 2026