Agent Description Protocol (ADP)

Autonomous AI agents in a decentralized network need a common way to describe their capabilities so that peers can discover and invoke them. The Agent Internet Protocol (AIP) provides name-based datagram delivery between agents identified by agent:// URIs; the Agent Invocation Transport Protocol (AITP) provides reliable invocation and streaming above AIP. This document describes the Agent Description Protocol (ADP), an application-layer convention carried over AITP that defines how agents describe their capabilities, publish those descriptions, and discover peers whose capabilities match a query. ADP defines the Agent Card, a JSON document format that carries an agent's identity, human-readable description, method catalogue, endpoint bindings, skill tags, and operational constraints. ADP also defines three AITP method names — adp.describe, adp.advertise, and adp.discover — through which agents exchange and query Agent Cards at the invocation layer. ADP is intentionally a thin format-and-convention layer: it standardizes the document schema and the exchange methods, but defers reputation, economics, credentials, identity infrastructure, and deployment-specific dissemination mechanisms (DHT topics, GossipSub channels, HTTP well-known URIs) to companion protocols and implementation profiles.