A2A and Multi-Agent Design

As agent deployments grow, a single agent often stops being enough. A customer may already have agents built by different teams, running on different frameworks, or supplied by different vendors. A billing agent built by the finance team, a network diagnostics agent built by operations, and a vendor’s scheduling agent may all need to work together to resolve one customer request. Connecting these agents requires a different kind of integration than connecting an agent to a database or an API.

The Agent2Agent (A2A) protocol addresses this need. Google introduced A2A in 2025 as an open standard for communication between agents and later contributed it to the Linux Foundation. FDE interviewers expect candidates to explain how A2A differs from MCP and, more importantly, to judge when a multi-agent design is justified. Splitting a system into many agents is easy to propose and often expensive to operate, so the ability to argue for or against it is a strong signal of design judgment.

How A2A differs from MCP

MCP and A2A solve different problems, and they are often used together. MCP connects an agent to tools and data. The agent calls a tool, receives a result, and stays in control of the reasoning. A2A connects an agent to another agent. The calling agent hands off a task, and the remote agent reasons, uses its own tools, and returns a result, sometimes after many steps and with follow-up questions along the way.

A useful way to remember the difference is that MCP treats the other side as an instrument, while A2A treats it as a ...