d0nghyun/api-slack

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|text> | | 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