A set of tools and procedures for reading and carefully managing Slack workspaces, including channels, messages, threads, files, and webhook signatures. Slack is a team communication platform.

Use it to search message history, read threads, inspect channels and files, verify webhook requests, and prepare or send confirmed replies.

It helps an agent find relevant conversations and shared files without losing context, while requiring confirmation before posting messages or changing shared data.

slack — Skill for Claude Code and Codex by magnus919

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.

Any agent

npx skills add magnus919/agent-skills --skill slack

Clone the repo

git clone --depth 1 https://github.com/magnus919/agent-skills

Made for: Claude Code, Codex.

Its marketplace also offers this one on its own, as the plugin slack — /plugin install slack after adding the marketplace above.

Wrote this? Show the measurements

A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.

README.md

[![agentmods](https://agentmods.dev/badge/skills/magnus919/agent-skills/slack/github.svg)](https://agentmods.dev/skills/magnus919/agent-skills/slack)

Your own site

<a href="https://agentmods.dev/skills/magnus919/agent-skills/slack"><img src="https://agentmods.dev/badge/skills/magnus919/agent-skills/slack/github.svg" alt="Measured on agentmods" height="20"></a>

Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.

Your own site · 80×15

<a href="https://agentmods.dev/skills/magnus919/agent-skills/slack"><img src="https://agentmods.dev/badge/skills/magnus919/agent-skills/slack.svg" alt="Reviewed on agentmods" width="80" height="20"></a>

Per session 120 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.

When invoked 2,221 The whole file, excluding the scripts and references it only reads on demand.

Security scan A 0 findings. A grade says what 26 rules found in the file — not that it is safe. Third-party audits

NVIDIA SkillSpector warn 7 Sept 2026

SkillSpector: 1 finding, up to medium

These are SkillSpector’s own severities. On a checked sample its high-severity flags on skills were ~96% false positives — a documented command, a public API, a “never do X” rule — so we show them as a caution to read, not a verdict. Why →

medium Data Exfiltration · line 20
Data is being sent to an external URL. This could be legitimate telemetry or data exfiltration. Manual review is recommended.

Fix: Verify the destination URL is trusted and necessary. Remove or replace with documented APIs. Ensure no secrets, tokens, or PII are transmitted.

How audits are shown

Origin original No closer match found 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.

Model	Per session	Once invoked
Fable 5.1	$0.00120	$0.02221
Opus 5	$0.00060	$0.01111
Sonnet 5	$0.00024	$0.00444
Haiku 4.5	$0.00012	$0.00222

Measured 6d ago against content hash 235cff4856f0, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-09, 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 6d ago.

The scan reads SKILL.md. This mod also ships 1 executable file (tests/test_slack_cli.py), listed below but not scanned — reading those needs a real analyzer, not pattern matching.

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.

slack/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.

Slack Operations

Use this skill to read and, with explicit confirmation, write Slack data through the Slack Web API: channels, messages, threads, search, files, and webhook signature verification. This is a tool skill for the Slack platform. Building Slack apps and bots is application development; workspace administration (user provisioning, org-level settings, SSO) lives in the Slack admin console. This skill owns the everyday agent workflow: knowing what was said, finding it later, and posting a reply when a human confirms.

Operating contract

Read-only discovery before any mutation. List channels, read history, follow threads, search, and list files freely. The bundled slack-cli script makes reads without writing anything.
Confirm the target, scope, and rollback path before acting. Sending a message or replying in a thread changes shared workspace state visible to everyone: it requires an explicit human directive naming the channel, plus --dry-run preview and --yes confirmation through slack-cli. There is no "unsend" for team members who already read it.
Respect bounded reads. Slack paginates; never page past what the task needs. slack-cli --limit N caps every listing, and responses summarize records rather than dumping raw payloads.
Verify webhooks before trusting them. Any handler that accepts Slack events must verify X-Slack-Signature and X-Slack-Request-Timestamp against the app signing secret, or anyone who can reach the endpoint can forge events. slack-cli webhook verify does this check.
Keep evidence bounded. Quote short message excerpts and IDs; never paste full threads, tokens, or file contents into chat.

The slack-cli script

scripts/slack-cli is an agent-first, stdlib-only CLI over the Slack Web API. It covers the full issue scope: messages, channels, threads, search, files, and webhook verification.

slack/scripts/slack-cli --help                          # no token or network needed
slack/scripts/slack-cli --json --limit 10 channels list
slack/scripts/slack-cli --json messages list --channel C12345
slack/scripts/slack-cli --json threads list --channel C12345 --ts 1712345678.000001
slack/scripts/slack-cli --json search messages --query "incident"
slack/scripts/slack-cli --json files list --limit 5
slack/scripts/slack-cli messages send --channel C12345 --text "on it" --dry-run   # preview
slack/scripts/slack-cli messages send --channel C12345 --text "on it" --yes       # confirmed
slack/scripts/slack-cli webhook verify --body-file body.json --signature "v0=..." --timestamp 1712345678

Read the full file on GitHub · 123 lines

Files

What ships with it

6 files beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.

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.

6d ago First seen · 123 lines · 120 tokens per session scan A 235cff4856f0

Subscribe to this mod's changes

slack is a skill published in the GitHub repository magnus919/agent-skills (76 stars, last pushed today), licensed MIT. It adds 120 tokens to every session and 2,221 once invoked, about $0.0006 per session on Opus 5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-09-03.

LLM Productivity agent-skills agentskills ai-agents automation

slack

Getting it into your agent

Wrote this? Show the measurements

What it costs to keep this loaded

Grade A, and why

Nothing flagged

How it starts

Slack Operations

Operating contract

The slack-cli script

What ships with it

What this file has done since we first saw it

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