# Slack Msg

> Post messages, list channels, and reply to threads via the Slack Web API.

- Skill: `qhkm/slack-msg` (Agent Skill, multi-file: 2 files)
- Install (CLI): `npx skillmds@latest add qhkm/slack-msg`
- Raw SKILL.md: https://api.skillmd.com/api/skills/qhkm/slack-msg/raw
- Safety review: pending
- Works with: Claude Code, Claude.ai, OpenAI Codex
- Category: Integrations & APIs
- License: MIT
- Author: qhkm (https://skillmd.com/u/qhkm)
- Updated: 2026-09-17
- Page: https://skillmd.com/skills/qhkm/slack-msg

---


# Slack Message Skill

Post messages, list channels, and reply to threads using the Slack Web API.

## Setup

1. Go to [api.slack.com/apps](https://api.slack.com/apps) → Create New App
2. Add Bot Token Scopes: `chat:write`, `channels:read`, `files:write`
3. Install app to workspace → Copy **Bot User OAuth Token**

```bash
export SLACK_BOT_TOKEN="xoxb-xxx..."
```

## Post a Message

```bash
curl -s -X POST "https://slack.com/api/chat.postMessage" \
  -H "Authorization: Bearer $SLACK_BOT_TOKEN" \
  -H "Content-Type: application/json" \
  -d '{
    "channel": "C0XXXXXX",
    "text": "Deploy completed successfully"
  }' | jq '{ok, ts: .ts, channel: .channel}'
```

## List Channels

```bash
curl -s "https://slack.com/api/conversations.list?types=public_channel&limit=50" \
  -H "Authorization: Bearer $SLACK_BOT_TOKEN" \
  | jq '.channels[] | {id, name, num_members}'
```

## Reply to a Thread

```bash
curl -s -X POST "https://slack.com/api/chat.postMessage" \
  -H "Authorization: Bearer $SLACK_BOT_TOKEN" \
  -H "Content-Type: application/json" \
  -d '{
    "channel": "C0XXXXXX",
    "thread_ts": "1234567890.123456",
    "text": "Thread reply from agent"
  }' | jq '{ok, ts}'
```

## Post with Blocks (Rich Formatting)

```bash
curl -s -X POST "https://slack.com/api/chat.postMessage" \
  -H "Authorization: Bearer $SLACK_BOT_TOKEN" \
  -H "Content-Type: application/json" \
  -d '{
    "channel": "C0XXXXXX",
    "blocks": [
      {"type": "header", "text": {"type": "plain_text", "text": "Daily Report"}},
      {"type": "section", "text": {"type": "mrkdwn", "text": "*Errors:* 3\n*Uptime:* 99.9%"}}
    ]
  }' | jq '{ok, ts}'
```

## Tips

- Channel IDs start with `C` (public) or `G` (private) — use IDs not names
- Bot must be invited to a channel before posting: `/invite @botname`
- Rate limit: ~1 message/second per channel (burst: 100 per minute)
- `thread_ts` is the timestamp of the parent message
- Slack uses `mrkdwn` (not markdown) — bold is `*text*`, italic is `_text_`