We run SAP AI Lab — two of us, one in ML systems, one in enterprise information systems, independent of both vendors whose acronyms appear below. When SAP put A2A at the center of its BTP agentic stack at TechEd Berlin 2025 and Microsoft shipped an A2A endpoint in Foundry Agent Service, we tried to connect the two and wrote down every wall we hit. All facts below re-verified against SAP and Microsoft documentation as of 2026-11-08.

First, one line of context for anyone arriving late: the Agent2Agent protocol is the open standard for agents calling other agents — an Agent Card published at /.well-known/agent-card.json , then tasks with a real lifecycle ( submitted → working → terminal states, with input-required for "a human must approve this"). It complements MCP rather than competing: MCP gives each agent depth against its tools, A2A gives the system reach across an organizational boundary.…