Protocols & Auth

The proto key (alias p) declares which protocol the agent endpoint speaks. The auth key (alias a) hints at the authentication method required. Both are defined in the Specification appendices.

Supported proto Tokens

AID v1.1 defines 9 protocol tokens. Remote protocols require https:// URIs (or wss:// for WebSocket). Local protocols use scheme-specific URIs.

mcp — Model Context Protocol

JSON-RPC endpoint implementing the Model Context Protocol. The most common token for AI agent discovery.

• URI scheme: https://
• Use case: LLM tool servers, AI assistants, coding agents

v=aid1;u=https://api.example.com/mcp;p=mcp;a=oauth2_code;s=AI Assistant

a2a — Agent-to-Agent Protocol

URL to an A2A AgentCard (agent.json). Used for agent-to-agent interoperability.

• URI scheme: https://
• Use case: Multi-agent orchestration, agent marketplaces

v=aid1;u=https://agent.example.com/.well-known/agent.json;p=a2a;s=Task Agent

openapi — OpenAPI Specification

URL to an OpenAPI document (JSON or YAML). Allows clients to discover and interact with REST APIs.

• URI scheme: https://
• Use case: Traditional REST APIs, API gateways, tools that generate client code

v=aid1;u=https://api.example.com/openapi.json;p=openapi;s=Public API

grpc — gRPC over HTTP/2

gRPC service endpoint. Clients connect using gRPC over HTTP/2 (or HTTP/3).

• URI scheme: https://
• Use case: High-performance inter-service communication, streaming, polyglot environments

v=aid1;u=https://grpc.example.com;p=grpc;a=mtls;s=Inference Service

graphql — GraphQL over HTTP

GraphQL endpoint. Clients send queries via HTTP POST (or GET for persisted queries).

• URI scheme: https://
• Use case: Flexible data queries, frontend-driven APIs, aggregation layers

v=aid1;u=https://api.example.com/graphql;p=graphql;a=pat;s=Data Gateway

websocket — WebSocket Transport

WebSocket endpoint for persistent, bidirectional communication.

• URI scheme: wss://
• Use case: Real-time streaming, chat agents, event-driven architectures

v=aid1;u=wss://ws.example.com/agent;p=websocket;s=Live Agent

local — Local Execution

The agent runs locally on the client machine. URI uses scheme-specific locators for the execution environment.

• URI schemes: docker:, npx:, pip:
• Use case: Development, offline agents, privacy-sensitive workloads
• Security: Requires explicit user consent before execution. See Security.

v=aid1;u=docker:myorg/agent:latest;p=local;s=Local Dev Agent
v=aid1;u=npx:@myorg/agent-cli;p=local;s=CLI Agent
v=aid1;u=pip:my-agent;p=local;s=Python Agent

zeroconf — mDNS/DNS-SD Service Discovery

Local network service discovery via mDNS/DNS-SD. Used to find agents on the same LAN.

• URI scheme: zeroconf:<service_type>
• Use case: IoT devices, local development environments, LAN-only agents

v=aid1;u=zeroconf:_mcp._tcp;p=zeroconf;s=Office Agent

ucp — Universal Commerce Protocol

Endpoint implementing the Universal Commerce Protocol for commercial agent transactions.

• URI scheme: https://
• Use case: E-commerce agents, payment flows, commercial service orchestration

v=aid1;u=https://commerce.example.com/ucp;p=ucp;a=oauth2_code;s=Commerce Agent

Protocol Summary

Auth Hints (auth)

The auth key (alias a) tells clients what authentication method to expect. It is a hint — the actual authentication flow is handled by the target protocol.

Example with auth

v=aid1;u=https://api.example.com/mcp;p=mcp;a=pat;s=Example MCP

Notes

• Publish short keys (p, a) as the canonical v1.x TXT format. Parsers still accept the full names for compatibility.
• desc/s is optional, max 60 UTF-8 bytes.
• Remote protocols MUST use https:// (or wss:// for websocket).
• local uses approved schemes only: docker:, npx:, pip:.
• Use the aid-doctor CLI to validate records and generate compliant configurations.

See Also

• Quick Start
• Troubleshooting
• Conformance