Agent Identity Protocol: Agentic Authentication and Authorized Policy Enforcement

This document defines the Agent Identity Protocol (AIP), an open standard for verifiable identity and policy enforcement for artificial intelligence (AI) agents. Agent Identity Protocol (AIP) addresses the problem of AI agents operating with unbounded permissions -- running as users, inheriting full API key access, and executing tool calls with no verifiable identity boundary between human and non-human actors. The protocol is structured as two cooperating layers. Layer 1 (Identity) gives every agent a unique identifier and a key pair registered with an AIP Registry; the agent signs every outbound action with that key. Layer 2 (Enforcement) interposes a proxy between the AI client and every tool server that verifies the signature, evaluates a declarative policy, and produces an allow, deny, or hold decision before any tool is reached.