AgentRFC: Security Design Principles and Conformance Testing for Agent Protocols

AI agent protocols -- including MCP, A2A, ANP, and ACP -- enable autonomous agents to discover capabilities, delegate tasks, and compose services across trust boundaries. Despite massive deployment (MCP alone has 97M+ monthly SDK downloads), no systematic security framework for these protocols exists. We present three contributions. First, the Agent Protocol Stack, a 6-layer architectural model that defines what a complete agent protocol must specify at each layer -- analogous to ITU-T X.800 for