Model Context Protocol (MCP) vs. Agent2Agent (A2A): which protocol do you need?

What this post added

Introduces and contrasts Model Context Protocol (MCP) and Agent2Agent (A2A) protocols for agent communication. MCP is described as an open standard for connecting LLM apps to external tools and data, using a hierarchical client-server model with roles for hosts, clients, and servers, and primitives like tools, resources, and prompts. A2A is presented as a protocol for communication between independent agents, featuring Agent Cards for discovery, stateful Tasks, and Artifacts, supporting peer-to-peer interaction and longer-running tasks. The post clarifies that MCP is for agent-to-tool integration and A2A is for agent-to-agent collaboration, with the decision hinging on agent ownership and trust boundaries. It also highlights that neither protocol fully addresses state correlation across workflows or end-to-end observability.