api-slack

name	api-slack
description	Slack Web API for messaging, channels, and notifications. Uses Bot token for headless/CI. Activate for Slack operations.
allowed-tools	Bash, Read, Grep
user-invocable	true
quality_grade	C
quality_checked	"2026-03-19T00:00:00.000Z"

Slack API Skill

When to Activate

• Send messages to channels or users
• Post notifications and alerts
• Manage channels
• Upload files
• Read channel history

Authentication

Credentials File: .credentials/slack.json

{
  "bot_token": "xoxb-...",
  "channel_id": "C..."
}

Create token at: https://api.slack.com/apps → Your App → OAuth & Permissions

Load credentials before API calls:

SLACK_BOT_TOKEN=$(jq -r '.bot_token' /Users/dhlee/Git/personal/neuron/.credentials/slack.json)
SLACK_CHANNEL_ID=$(jq -r '.channel_id' /Users/dhlee/Git/personal/neuron/.credentials/slack.json)

Required Scopes:

• chat:write - Send messages
• channels:read - List public channels
• channels:history - Read public channel messages
• groups:history - Read private channel messages
• files:write - Upload files
• reactions:read - Read reactions (optional)

API Base URL

https://slack.com/api

Required Headers

-H "Authorization: Bearer $SLACK_BOT_TOKEN"
-H "Content-Type: application/json"

Common Operations

Test Authentication

curl -s -X POST \
  -H "Authorization: Bearer $SLACK_BOT_TOKEN" \
  "https://slack.com/api/auth.test"

Send Message

curl -s -X POST \
  -H "Authorization: Bearer $SLACK_BOT_TOKEN" \
  -H "Content-Type: application/json" \
  -d '{
    "channel": "CHANNEL_ID",
    "text": "Hello from Claude!"
  }' \
  "https://slack.com/api/chat.postMessage"

Send Message with Blocks (Rich Formatting)

curl -s -X POST \
  -H "Authorization: Bearer $SLACK_BOT_TOKEN" \
  -H "Content-Type: application/json" \
  -d '{
    "channel": "CHANNEL_ID",
    "blocks": [
      {
        "type": "section",
        "text": {
          "type": "mrkdwn",
          "text": "*Title*\nDescription text"
        }
      }
    ]
  }' \
  "https://slack.com/api/chat.postMessage"

List Channels

curl -s -X GET \
  -H "Authorization: Bearer $SLACK_BOT_TOKEN" \
  "https://slack.com/api/conversations.list?types=public_channel,private_channel"

Get Channel History

curl -s -X GET \
  -H "Authorization: Bearer $SLACK_BOT_TOKEN" \
  "https://slack.com/api/conversations.history?channel=CHANNEL_ID&limit=10"

Upload File

curl -s -X POST \
  -H "Authorization: Bearer $SLACK_BOT_TOKEN" \
  -F "channels=CHANNEL_ID" \
  -F "file=@/path/to/file" \
  -F "initial_comment=File description" \
  "https://slack.com/api/files.upload"

Reply in Thread

curl -s -X POST \
  -H "Authorization: Bearer $SLACK_BOT_TOKEN" \
  -H "Content-Type: application/json" \
  -d '{
    "channel": "CHANNEL_ID",
    "thread_ts": "1234567890.123456",
    "text": "Thread reply"
  }' \
  "https://slack.com/api/chat.postMessage"

Add Reaction

curl -s -X POST \
  -H "Authorization: Bearer $SLACK_BOT_TOKEN" \
  -H "Content-Type: application/json" \
  -d '{
    "channel": "CHANNEL_ID",
    "timestamp": "1234567890.123456",
    "name": "thumbsup"
  }' \
  "https://slack.com/api/reactions.add"

Message Formatting (mrkdwn)

Format	Syntax
Bold	*bold*
Italic	_italic_
Strike	~strike~
Code	`code`
Code block	```code```
Link	`<https://url
User mention	<@USER_ID>
Channel mention	<#CHANNEL_ID>

Error Handling

Error	Meaning	Action
invalid_auth	Bad token	Check .credentials/slack.json
channel_not_found	Invalid channel	Verify channel ID
not_in_channel	Bot not in channel	Invite bot to channel
ratelimited	Too many requests	Wait and retry

Rate Limits

• Tier 1: 1 request per second
• Tier 2: 20 requests per minute
• Tier 3: 50 requests per minute

Implement exponential backoff on ratelimited responses.

References

• Slack Web API
• Block Kit Builder
• Message Formatting