agent-messaging

A skill for sending and receiving cryptographically signed messages between AI agents through the Agent Messaging Protocol (AMP). It supports local or remote messaging, file attachments, identity checks, and message-provider registrations.

In plain words
What is it for?
Use it to check an agent inbox, send or reply to messages, register with messaging providers, download attachments, and inspect agent identity or messaging status.
Why use it?
It lets agents communicate and verify who sent a message instead of relying on informal, unsigned exchanges.

Skill for Claude CodeCodex

Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

agentmods
npx agentmods add skills/agentmessaging/claude-plugin/agent-messaging
Any agent
npx skills add agentmessaging/claude-plugin --skill agent-messaging
Clone the repo
git clone --depth 1 https://github.com/agentmessaging/claude-plugin

Made for: Claude Code, Codex.

Per session 50 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 2,524 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 1 finding. Scan, not verified.
Origin 100% copy Near-identical to another mod in the catalogue.
Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

ModelPer sessionOnce invoked
Fable 5 $0.00050 $0.02524
Opus 5 $0.00025 $0.01262
Sonnet 5 $0.00010 $0.00505
Haiku 4.5 $0.00005 $0.00252

Measured 2d ago against content hash 3176634fafb0, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

agent-messaging scanned grade A with 1 finding against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 2d ago.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Makes network callslowCapability

Not a fault in itself. Listed so you know the mod talks to something, and to what.

compatibility: Requires curl, jq, openssl, and base64 CLI tools. macOS and Linux supported. Scripts are POSIX-compatible bash.
Origin

This is a copy

100% identical to agent-messaging — 0 lines differ, which has more behind it and is treated as the original. This page carries a canonical link to it rather than competing with it.

skills/agent-messaging/SKILL.md · 331 lines

How it starts

The opening of the file, as written. The whole thing — 331 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Agent Messaging Protocol (AMP)

Send and receive messages with other AI agents using the Agent Messaging Protocol.

When to use this skill

Use this skill when the user or task requires:

  • Sending messages to other AI agents (local or remote)
  • Checking an inbox for incoming messages
  • Replying to messages from other agents
  • Registering with external messaging providers
  • Downloading file attachments from messages
  • Checking agent identity or messaging status

Agent Identification (--id)

Every command (except amp-init.sh) accepts --id <uuid> to specify which agent you're operating as. The UUID comes from the agent's config.json (agent.id field).

# Operate as a specific agent
amp-inbox.sh --id 6bbdaeb8-8a85-4d0b-8f8c-3c217486eae8
amp-send.sh --id <uuid> alice "Hello" "Hi there"

Resolution order (first match wins):

  1. AMP_DIR env var (AI Maestro sets this)
  2. --id <uuid> argument
  3. CLAUDE_AGENT_ID env var
  4. CLAUDE_AGENT_NAME env var / tmux session
  5. Single agent auto-select (if only one agent exists)

If multiple agents exist and none of the above resolve, the CLI lists available agents with UUIDs.

Identity Check (Run First)

Before using any messaging commands, ALWAYS verify your identity:

amp-identity.sh
# Or with explicit agent:
amp-identity.sh --id <uuid>

If you see "Not initialized", run:

amp-init.sh --auto

This identity check is essential because:

  • Your AMP identity persists across sessions
  • After context reset, you need to rediscover who you are
  • Each agent has its own isolated AMP directory with identity, keys, and messages

Identity file location: ${AMP_DIR}/IDENTITY.md (per-agent, auto-resolved)

Quick Start

# 1. Initialize (first time only)
amp-init.sh --auto

# 2. Send a message
amp-send.sh alice "Hello" "How are you?"

# 3. Check inbox
amp-inbox.sh

Installation

For Claude Code (plugin)

git clone https://github.com/agentmessaging/claude-plugin.git ~/.claude/plugins/agent-messaging

Read the full file on GitHub · 331 lines

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

  1. 2d ago First seen · 331 lines · 50 tokens per session scan A 3176634fafb0

Subscribe to this mod's changes

agent-messaging is a skill published in the GitHub repository agentmessaging/claude-plugin (5 stars, last pushed 14d ago), licensed Apache-2.0. It adds 50 tokens to every session and 2,524 once invoked, about $0.0003 per session on Opus 5. A static security scan graded it A with 1 finding (makes network calls). It is 100% identical to agent-messaging, differing in 0 lines, and is treated as a copy.

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