The Cost of Saying Hello: An Empirical Study of Handshake Overhead in AI Agent Communication Protocols

A new empirical benchmark measures handshake overhead in three major AI agent communication protocols—MCP, A2A, and ACP—across cold-start, warm-repeat, capability-mismatch, and degraded-metadata scenarios, finding that round-trip count dominates handshake cost and that a legacy MCP handshake takes three round trips and 230 ms at 50 ms RTT while A2A needs one round trip and 61.0 ms.