ACP — Agent Communication Protocol

The missing link between AI Agents.

Send a URL. Get a link. Two agents talk. That's it.

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MCP standardized Agent↔Tool. ACP standardizes Agent↔Agent.
P2P · Zero server required · curl-compatible · works with any LLM framework

What is ACP?

ACP is a lightweight, open protocol for direct Agent-to-Agent communication. Unlike enterprise solutions that require OAuth, service registries, and devops teams, ACP gives you:

• 🔗 A shareable link — paste it to any other agent to connect
• ⚡ Real-time messaging — SSE stream, sub-millisecond latency
• 🔒 True P2P — Relay only punches holes, never stores messages
• 🛠️ curl-compatible — any language, any framework, any LLM

60-Second Demo

# Terminal 1 — Agent A
python3 acp_relay.py --name AgentA
# ✅ Ready. Your link: acp://1.2.3.4:7801/tok_xxxxx

# Terminal 2 — Agent B: connect
curl -X POST http://localhost:7901/peers/connect \
     -d '{"link":"acp://1.2.3.4:7801/tok_xxxxx"}'
# {"ok":true,"peer_id":"peer_001"}

# Agent B: send a message
curl -X POST http://localhost:7901/message:send \
     -d '{"role":"agent","parts":[{"type":"text","content":"Hello AgentA!"}]}'
# {"ok":true,"message_id":"msg_abc123"}

# Agent A: receive via SSE stream
curl http://localhost:7901/stream
# event: acp.message
# data: {"role":"agent","parts":[{"type":"text","content":"Hello AgentA!"}]}

Why ACP?

	A2A (Enterprise)	ACP (Personal/Team)
Deploy	Ops team required	Zero server, local Skill
Connect	Code + config + registry	One link, paste & go
Auth	OAuth 2.0 full suite	Token in link, HMAC optional
Privacy	Through server	True P2P, relay stores nothing
Analogy	Enterprise ESB	WhatsApp for Agents

Key Features

P2P CommunicationAgentCardTask TrackingPython SDK

Three-level NAT traversal, fully transparent to your application:

Level 1: Direct WebSocket P2P
    ↓ fails 3×
Level 2: DCUtR UDP hole punching
    ↓ fails (symmetric NAT ~25%)
Level 3: Cloudflare Worker relay (100% fallback)

Full capability declaration in one JSON response:

curl http://localhost:7901/.well-known/acp.json

{
  "name": "AgentA",
  "version": "2.8.0",
  "capabilities": {"streaming": true, "hmac_signing": true},
  "limitations": ["no_file_access"],
  "extensions": [{"uri": "acp:ext:hmac-v1"}]
}

Built-in task state machine with SSE events:

submitted → working → completed
                   → failed
                   → cancelling → canceled
                   → input_required

from acp_client import RelayClient

c = RelayClient("http://localhost:7901")
link = c.status()["link"]

# Connect and send
peer = c.connect("acp://remote:7801/tok_xxx")
c.send("Hello!", peer_id=peer)

# Receive
for msg in c.stream():
    print(msg.parts[0].content)

Getting Started

• Quick Start

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  Get two agents talking in under 60 seconds.

  Quick Start

• Installation

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  Install the relay and Python SDK.

  Installation

• Core Concepts

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  Understand links, peers, tasks, and streams.

  Concepts

• vs. A2A

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  How ACP compares to Google's A2A protocol.

  Comparison

Version

Current stable: v3.17.2 — POST /messages:stream WebSocket streaming inlet with public launch hardening for CI, packaging, docs, Docker publishing, CodeQL, OpenSSF Scorecard, and standard Apache-2.0 license detection; see CHANGELOG for full history. See What's New · Compatibility Matrix · Roadmap.