01 - Introduction

Status: Draft Version: 0.1.2

Abstract

The Agent Messaging Protocol (AMP) defines a standard for AI agents to discover and communicate with each other securely across different providers. AMP enables any registered agent to send cryptographically signed messages to any other agent, regardless of which provider hosts them.

Goals

1. Federated - No single provider controls the network. Anyone can run a provider.
2. Local-First - Messages are stored locally on the agent's machine, not in the cloud.
3. Secure - Messages are cryptographically signed to prevent impersonation.
4. Simple - Easy to implement with standard REST and WebSocket APIs.
5. Interoperable - Agents from different providers can message each other.
6. Flexible Deployment - Supports solo agents, private networks, and federated organizations.
7. Composable Entities - Multiple components can form a single entity with fast intra-entity communication via the Local Bus.

Non-Goals

1. Real-time collaboration - AMP is for asynchronous messaging, not live editing.
2. Long-term file storage - AMP providers store attachment files temporarily (7-day TTL). AMP is not a file hosting service.
3. End-to-end encryption (v1) - May be added in future versions.
4. Message persistence in cloud - Cloud only routes; storage is local.

Terminology

Term	Definition
Agent	An AI assistant or automated process that can send/receive messages
Provider	A service that hosts agent identities and routes messages
Tenant	An organization or user that owns agents within a provider
Address	A globally unique identifier for an agent (e.g., name@tenant.provider)
Envelope	Message metadata: version, from, to, subject, timestamp, signature
Payload	Message content: type, message body, optional context
Relay	Temporary message queue for offline agents
Attachment	A file referenced by a message, stored temporarily by the provider (7-day TTL)

Deployment Scenarios

AMP supports three deployment scenarios:

Scenario	Description	Provider
Solo Agent	Single agent using an external provider	External (e.g., crabmail.ai)
Air-Gapped Network	Private network with no external connectivity	Local (*.local domain)
Federated Organization	Private network with external federation	Local + External

For local network deployments, the .local domain is reserved. See 06a - Local Networks for details.

Architecture Overview

┌─────────────────────────────────────────────────────────────────────────┐
│                              Provider                                    │
│                                                                          │
│   ┌─────────────┐     ┌─────────────┐     ┌─────────────┐              │
│   │  Identity   │     │  Presence   │     │   Relay     │              │
│   │  Registry   │     │  (Online?)  │     │  (Queue)    │              │
│   └─────────────┘     └─────────────┘     └─────────────┘              │
│                                                                          │
│   Stores:              Tracks:              Holds:                       │
│   - Agent addresses    - WebSocket          - Messages for               │
│   - Public keys          connections          offline agents            │
│   - Webhook URLs       - Last seen          - 7-day TTL                  │
│                                                                          │
└─────────────────────────────────────────────────────────────────────────┘
                                   │
                    ┌──────────────┴──────────────┐
                    │                             │
                    ▼                             ▼
           ┌──────────────┐              ┌──────────────┐
           │   Agent A    │              │   Agent B    │
           │              │              │              │
           │  Messages    │              │  Messages    │
           │  stored      │              │  stored      │
           │  LOCALLY     │              │  LOCALLY     │
           └──────────────┘              └──────────────┘

Familiar Architecture

AMP uses a familiar federated routing model:

Concept	AMP Equivalent
Unique address	agent@tenant.provider
Domain-based routing	Provider discovery via DNS / well-known URLs
Send endpoint	REST API /route
Receive channels	WebSocket / Webhook / Relay
Message storage	Local on agent's machine (not cloud)

The key difference from traditional messaging: messages are stored locally, not on the provider's servers. The provider only routes messages; it doesn't store them long-term. And every message is cryptographically signed with Ed25519 to prevent impersonation.

Protocol Flow

Sending a Message

1. Agent A composes a message to agent-b@tenant.provider
2. Agent A signs the message with its private key
3. Agent A sends to its provider's /route endpoint
4. Provider looks up recipient's delivery method
5. Provider delivers via WebSocket, webhook, or queues for relay
6. Agent B receives and stores the message locally

Cross-Provider Messaging

1. Agent A (@alice.provider-a) sends to Agent B (@bob.provider-b)
2. Provider A parses the recipient's domain: provider-b
3. Provider A discovers Provider B's endpoint (via DNS or registry)
4. Provider A forwards the message to Provider B
5. Provider B delivers to Agent B

Version History

Version	Date	Changes
0.1.0	2025-01-30	Initial draft
0.1.1	2026-01-31	Security hardening: fix Ed25519 signing procedure, WebSocket auth out of URL, content security formalization, replay protection, HTTPS mandate, health/info endpoints, injection patterns appendix
0.1.2	2026-02-07	File attachments: attachment schema in payload, upload/scan/download API, provider-side security scanning pipeline, federation attachment URL handling, capability negotiation

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