slack

A set of instructions for controlling Slack messages, reactions, pins, member information, and custom emojis through an assistant.

In plain words
What is it for?
Use it to read, send, edit, or delete messages; react to posts; manage pins; and look up members or emojis.
Why use it?
It avoids needing separate manual steps for common Slack actions when the channel and message details are known.

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

Made for: Claude Code, Codex.

Per session 36 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 735 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
Origin 77% 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 $0.00036 $0.00735
Opus 5 $0.00018 $0.00367
Sonnet 5 $0.00007 $0.00147
Haiku 4.5 $0.00004 $0.00073

Measured 2d ago against content hash 530077c0207e, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

slack 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

77% identical to slack — 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/slack/SKILL.md · 145 lines

How it starts

The opening of the file, as written. The whole thing — 145 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Slack Actions

Overview

Use slack to react, manage pins, send/edit/delete messages, and fetch member info. The tool uses the bot token configured for Understudy.

Inputs to collect

  • channelId and messageId (Slack message timestamp, e.g. 1712023032.1234).
  • For reactions, an emoji (Unicode or :name:).
  • For message sends, a to target (channel:<id> or user:<id>) and content.

Message context lines include slack message id and channel fields you can reuse directly.

Actions

Action groups

Action group Default Notes
reactions enabled React + list reactions
messages enabled Read/send/edit/delete
pins enabled Pin/unpin/list
memberInfo enabled Member info
emojiList enabled Custom emoji list

React to a message

{
  "action": "react",
  "channelId": "C123",
  "messageId": "1712023032.1234",
  "emoji": "✅"
}

List reactions

{
  "action": "reactions",
  "channelId": "C123",
  "messageId": "1712023032.1234"
}

Send a message

{
  "action": "sendMessage",
  "to": "channel:C123",
  "content": "Hello from Understudy"
}

Edit a message

{
  "action": "editMessage",
  "channelId": "C123",
  "messageId": "1712023032.1234",
  "content": "Updated text"
}

Delete a message

{
  "action": "deleteMessage",
  "channelId": "C123",
  "messageId": "1712023032.1234"
}

Read recent messages

{
  "action": "readMessages",
  "channelId": "C123",
  "limit": 20
}

Pin a message

{
  "action": "pinMessage",
  "channelId": "C123",
  "messageId": "1712023032.1234"
}

Unpin a message

{
  "action": "unpinMessage",
  "channelId": "C123",
  "messageId": "1712023032.1234"
}

List pinned items

{
  "action": "listPins",
  "channelId": "C123"
}

Member info

Read the full file on GitHub · 145 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 · 145 lines · 36 tokens per session scan A 530077c0207e

Subscribe to this mod's changes

slack is a skill published in the GitHub repository understudy-ai/understudy (456 stars, last pushed 2mo ago), licensed MIT. It adds 36 tokens to every session and 735 once invoked, about $0.0002 per session on Opus 5. A static security scan graded it A with 0 findings. It is 77% identical to slack, differing in 8 lines, and is treated as a copy.