The agent:// Protocol -- A URI-Based Framework for Interoperable Agents

This document defines the agent:// protocol, a URI-based addressing scheme for identifying, discovering, and invoking autonomous and semi-autonomous software agents. The agent:// scheme provides a semantic layer that signals "this resource is an agent" and enables agent-specific discovery via standardized descriptors. It introduces a layered architecture with four conformance levels, allowing implementations to adopt minimal addressing (Level 0) or full descriptor-based discovery with authentication and versioning (Level 3). The protocol complements existing agent communication protocols such as Agent2Agent (A2A), Model Context Protocol (MCP), and Agent Communication Protocol (ACP) by providing the addressing and discovery layer they lack.