The Model Context Protocol (MCP) and Agent 2 Agent (A2A) specification are similar RPC style protocols that specify interaction between Agents and Tools (MCP) and Agents and other Agents (A2A). They both focus on client/server remote function invocations but do not specify protocol-specific security. MCP started to dip its toes into specifying an Authorization framework, but that has been a bumpy ride so far.
