imsg

A command-line tool for reading and sending iMessage and SMS through Apple's Messages app on macOS.

In plain words
What is it for?
Use it to check chat history, read recent conversations, and send messages to phone numbers or Apple IDs. It requires Messages to be signed in and appropriate macOS permissions.
Why use it?
It lets scripts and coding agents work with Messages conversations without manually searching and typing in the app.

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/understudy-ai/understudy/imsg
Any agent
npx skills add understudy-ai/understudy --skill imsg
Clone the repo
git clone --depth 1 https://github.com/understudy-ai/understudy

Made for: Claude Code, Codex.

Per session 21 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 772 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
Origin 94% 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 $0.00021 $0.00772
Opus 5 $0.00010 $0.00386
Sonnet 5 $0.00004 $0.00154
Haiku 4.5 $0.00002 $0.00077

Measured 2d ago against content hash e1593863ca5b, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

imsg scanned grade A with 0 findings 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.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

Origin

This is a copy

94% identical to imsg — 8 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/imsg/SKILL.md · 123 lines

How it starts

The opening of the file, as written. The whole thing — 123 lines — stays where its author put it; the contents beside it link to each section on GitHub.

imsg

Use imsg to read and send iMessage/SMS via macOS Messages.app.

When to Use

USE this skill when:

  • User explicitly asks to send iMessage or SMS
  • Reading iMessage conversation history
  • Checking recent Messages.app chats
  • Sending to phone numbers or Apple IDs

When NOT to Use

DON'T use this skill when:

  • Telegram messages → use message_send with channel: "telegram"
  • Signal messages → use Signal channel if configured
  • WhatsApp messages → use WhatsApp channel if configured
  • Discord messages → use message_send with channel: "discord"
  • Slack messages → use slack skill
  • Group chat management (adding/removing members) → not supported
  • Bulk/mass messaging → always confirm with user first
  • Replying in current conversation → just reply normally (Understudy routes automatically)

Requirements

  • macOS with Messages.app signed in
  • Full Disk Access for terminal
  • Automation permission for Messages.app (for sending)

Common Commands

List Chats

imsg chats --limit 10 --json

View History

# By chat ID
imsg history --chat-id 1 --limit 20 --json

# With attachments info
imsg history --chat-id 1 --limit 20 --attachments --json

Watch for New Messages

imsg watch --chat-id 1 --attachments

Send Messages

# Text only
imsg send --to "+14155551212" --text "Hello!"

# With attachment
imsg send --to "+14155551212" --text "Check this out" --file /path/to/image.jpg

# Specify service
imsg send --to "+14155551212" --text "Hi" --service imessage
imsg send --to "+14155551212" --text "Hi" --service sms

Service Options

  • --service imessage — Force iMessage (requires recipient has iMessage)
  • --service sms — Force SMS (green bubble)
  • --service auto — Let Messages.app decide (default)

Safety Rules

  1. Always confirm recipient and message content before sending
  2. Never send to unknown numbers without explicit user approval
  3. Be careful with attachments — confirm file path exists
  4. Rate limit yourself — don't spam

Read the full file on GitHub · 123 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 · 123 lines · 21 tokens per session scan A e1593863ca5b

Subscribe to this mod's changes

imsg is a skill published in the GitHub repository understudy-ai/understudy (456 stars, last pushed 2mo ago), licensed MIT. It adds 21 tokens to every session and 772 once invoked, about $0.0001 per session on Opus 5. A static security scan graded it A with 0 findings. It is 94% identical to imsg, differing in 8 lines, and is treated as a copy.