Tsinghua University Zhongguancun Laboratory Zhongguancun Laboratory This document proposes a standardized protocol for discovery and invocation of AI agents. It defines a common metadata format for describing AI agents (including capabilities, I/O specifications, supported languages, tags, authentication methods, etc.), a capability-based discovery mechanism, and a unified RESTful invocation interface. This revision additionally specifies an optional extension that enables intent-based agent selection prior to discovery and invocation, without changing existing discovery or invocation semantics. The goal is to enable cross-platform interoperability among AI agents by providing a discover-and-match mechanism and a unified invocation entry point. Security considerations, including authentication and trust measures, are also discussed. This specification aims to facilitate the formation of multi-agent systems by making it easy to find the right agent for a task and invoke it in a consistent manner across different vendors and platforms.