A2A Is Not MCP: Routing Messages Is Not the Same as Scheduling Work

Protocols move messages. Control planes decide what runs, where, and under which constraints. If you build multi-agent systems in production, this distinction matters than most architecture diagrams admit. A2A-style protocols are useful. They let agents exchange messages, advertise capabilities, and interoperate across boundaries. That is real value. But a message protocol is not the same thing as a control plane.