Slack Notifications Skill

Overview

This skill provides Slack API operations with progressive disclosure for optimal context usage.

Context Savings: ~90% reduction

• MCP Mode: ~15,000 tokens always loaded (30+ tools)
• Skill Mode: ~500 tokens metadata + on-demand loading

Requirements

• SLACK_BOT_TOKEN environment variable (required)
• SLACK_SIGNING_SECRET environment variable (optional, for event verification)
• SLACK_APP_TOKEN environment variable (optional, for Socket Mode)

Setting up Slack Bot Token

1. Create a Slack App at https://api.slack.com/apps
2. Navigate to "OAuth & Permissions"
3. Add required bot token scopes:
   • chat:write - Send messages
   • channels:read - List channels
   • channels:history - Read channel history
   • users:read - List users
   • files:write - Upload files
   • reactions:write - Add reactions
4. Install app to workspace
5. Copy "Bot User OAuth Token" to SLACK_BOT_TOKEN environment variable

Tools

The skill provides 14 tools across 5 categories:

Category	Tools	Confirmation Required
Messaging	post-message, post-thread, update-message, delete-message	Yes (all)
Channels	list-channels, get-channel, channel-history	No
Users	list-users, get-user, user-presence	No
Files	upload-file, list-files	Yes (upload only)
Reactions	add-reaction, get-reactions	No

Quick Reference

# Post message to channel
curl -X POST https://slack.com/api/chat.postMessage \
  -H "Authorization: Bearer $SLACK_BOT_TOKEN" \
  -H "Content-Type: application/json" \
  -d '{"channel": "C1234567890", "text": "Hello from Claude!"}'

# List channels
curl -X GET "https://slack.com/api/conversations.list" \
  -H "Authorization: Bearer $SLACK_BOT_TOKEN"

# Upload file
curl -X POST https://slack.com/api/files.upload \
  -H "Authorization: Bearer $SLACK_BOT_TOKEN" \
  -F "channels=C1234567890" \
  -F "file=@report.pdf" \
  -F "title=Weekly Report"

Tool Details

Messaging Tools (Confirmation Required)

post-message

Send a message to a Slack channel.

Parameters:

• channel (required): Channel ID or name (e.g., "C1234567890" or "#general")
• text (required): Message text (supports Slack markdown)
• thread_ts (optional): Parent message timestamp for threading
• blocks (optional): Rich message blocks (JSON array)

Example:

curl -X POST https://slack.com/api/chat.postMessage \
  -H "Authorization: Bearer $SLACK_BOT_TOKEN" \
  -H "Content-Type: application/json" \
  -d '{
    "channel": "C1234567890",
    "text": "Deployment successful!",
    "blocks": [
      {
        "type": "section",
        "text": {
          "type": "mrkdwn",
          "text": "*Deployment Status*\n:white_check_mark: Production deployed successfully"
        }
      }
    ]
  }'

post-thread

Reply to a message in a thread.

Parameters:

• channel (required): Channel ID
• thread_ts (required): Parent message timestamp
• text (required): Reply text

Example:

curl -X POST https://slack.com/api/chat.postMessage \
  -H "Authorization: Bearer $SLACK_BOT_TOKEN" \
  -H "Content-Type: application/json" \
  -d '{
    "channel": "C1234567890",
    "thread_ts": "1234567890.123456",
    "text": "Thread reply here"
  }'

update-message

Update an existing message.

Parameters:

• channel (required): Channel ID
• ts (required): Message timestamp
• text (required): New message text

Example:

curl -X POST https://slack.com/api/chat.update \
  -H "Authorization: Bearer $SLACK_BOT_TOKEN" \
  -H "Content-Type: application/json" \
  -d '{
    "channel": "C1234567890",
    "ts": "1234567890.123456",
    "text": "Updated message"
  }'

delete-message

Delete a message.

Parameters:

• channel (required): Channel ID
• ts (required): Message timestamp

Example:

curl -X POST https://slack.com/api/chat.delete \
  -H "Authorization: Bearer $SLACK_BOT_TOKEN" \
  -H "Content-Type: application/json" \
  -d '{
    "channel": "C1234567890",
    "ts": "1234567890.123456"
  }'

Channel Tools

list-channels

List all channels in workspace.

Parameters:

• types (optional): Comma-separated channel types (default: "public_channel")
  • Options: "public_channel", "private_channel", "mpim", "im"
• limit (optional): Max channels to return (default: 100)

Example:

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

get-channel

Get channel information.

Parameters:

• channel (required): Channel ID

Example:

curl -X GET "https://slack.com/api/conversations.info?channel=C1234567890" \
  -H "Authorization: Bearer $SLACK_BOT_TOKEN"

channel-history

Get channel message history.

Parameters:

• channel (required): Channel ID
• limit (optional): Max messages to return (default: 100)
• oldest (optional): Start of time range (Unix timestamp)
• latest (optional): End of time range (Unix timestamp)

Example:

curl -X GET "https://slack.com/api/conversations.history?channel=C1234567890&limit=50" \
  -H "Authorization: Bearer $SLACK_BOT_TOKEN"

Security Note: Channel history may contain sensitive information. Use with caution.

User Tools

list-users

List all users in workspace.

Parameters:

• limit (optional): Max users to return (default: 100)

Example:

curl -X GET "https://slack.com/api/users.list" \
  -H "Authorization: Bearer $SLACK_BOT_TOKEN"

get-user

Get user profile information.

Parameters:

• user (required): User ID

Example:

curl -X GET "https://slack.com/api/users.info?user=U1234567890" \
  -H "Authorization: Bearer $SLACK_BOT_TOKEN"

user-presence

Get user online status.

Parameters:

• user (required): User ID

Example:

curl -X GET "https://slack.com/api/users.getPresence?user=U1234567890" \
  -H "Authorization: Bearer $SLACK_BOT_TOKEN"

File Tools

upload-file (Confirmation Required)

Upload a file to Slack channel.

Parameters:

• channels (required): Comma-separated channel IDs
• file (required): File path to upload
• title (optional): File title
• initial_comment (optional): Message text

Example:

curl -X POST https://slack.com/api/files.upload \
  -H "Authorization: Bearer $SLACK_BOT_TOKEN" \
  -F "channels=C1234567890" \
  -F "file=@C:\reports\weekly.pdf" \
  -F "title=Weekly Report" \
  -F "initial_comment=Here is this week's report"

list-files

List files in channel.

Parameters:

• channel (optional): Channel ID to filter by
• user (optional): User ID to filter by
• count (optional): Max files to return (default: 100)

Example:

curl -X GET "https://slack.com/api/files.list?channel=C1234567890" \
  -H "Authorization: Bearer $SLACK_BOT_TOKEN"

Reaction Tools

add-reaction

Add emoji reaction to a message.

Parameters:

• channel (required): Channel ID
• timestamp (required): Message timestamp
• name (required): Emoji name (without colons, e.g., "thumbsup")

Example:

curl -X POST https://slack.com/api/reactions.add \
  -H "Authorization: Bearer $SLACK_BOT_TOKEN" \
  -H "Content-Type: application/json" \
  -d '{
    "channel": "C1234567890",
    "timestamp": "1234567890.123456",
    "name": "thumbsup"
  }'

get-reactions

Get reactions on a message.

Parameters:

• channel (required): Channel ID
• timestamp (required): Message timestamp

Example:

curl -X GET "https://slack.com/api/reactions.get?channel=C1234567890&timestamp=1234567890.123456" \
  -H "Authorization: Bearer $SLACK_BOT_TOKEN"

Agent Integration

Primary Agents

• devops: Infrastructure alerts, deployment notifications, monitoring
• incident-responder: Incident alerts, status updates, escalations

Secondary Agents

• pm: Sprint notifications, milestone updates, team announcements
• developer: Build notifications, PR alerts, test results
• qa: Test failure alerts, quality reports
• security-architect: Security alerts, vulnerability notifications

Common Use Cases

Deployment Notifications

# Notify channel of successful deployment
curl -X POST https://slack.com/api/chat.postMessage \
  -H "Authorization: Bearer $SLACK_BOT_TOKEN" \
  -H "Content-Type: application/json" \
  -d '{
    "channel": "#deployments",
    "text": ":rocket: Production deployment completed",
    "blocks": [
      {
        "type": "section",
        "text": {
          "type": "mrkdwn",
          "text": "*Production Deployment*\n:white_check_mark: v1.2.3 deployed successfully\n*Duration:* 5m 23s"
        }
      }
    ]
  }'

Incident Alerts

# Alert on-call team of incident
curl -X POST https://slack.com/api/chat.postMessage \
  -H "Authorization: Bearer $SLACK_BOT_TOKEN" \
  -H "Content-Type: application/json" \
  -d '{
    "channel": "#incidents",
    "text": "<!channel> :rotating_light: High severity incident detected",
    "blocks": [
      {
        "type": "section",
        "text": {
          "type": "mrkdwn",
          "text": "*Incident INC-1234*\n:rotating_light: *Severity:* P1\n*Service:* API Gateway\n*Status:* 503 errors increasing"
        }
      }
    ]
  }'

Test Results

# Post test results
curl -X POST https://slack.com/api/chat.postMessage \
  -H "Authorization: Bearer $SLACK_BOT_TOKEN" \
  -H "Content-Type: application/json" \
  -d '{
    "channel": "#qa",
    "text": "Test suite completed",
    "blocks": [
      {
        "type": "section",
        "text": {
          "type": "mrkdwn",
          "text": "*Test Results*\n:white_check_mark: 245 passed\n:x: 3 failed\n:warning: 2 skipped"
        }
      }
    ]
  }'

Security Considerations

Token Security

• NEVER expose bot token in logs or error messages
• Store token in environment variable, not in code
• Use least-privilege scopes for bot token
• Rotate tokens periodically

Message Security

• All message operations require confirmation
• Channel history may contain sensitive information (PII, credentials, etc.)
• Validate channel permissions before posting
• Use private channels for sensitive communications

Data Privacy

• Comply with workspace data retention policies
• Avoid posting PII or credentials in messages
• Use Slack's data export features for compliance
• Respect user privacy and online status

Error Handling

Common Errors

Error	Cause	Solution
not_authed	Missing or invalid token	Check SLACK_BOT_TOKEN is set correctly
channel_not_found	Invalid channel ID	Verify channel ID with list-channels
missing_scope	Bot lacks required permission	Add scope in Slack App settings
rate_limited	Too many requests	Implement exponential backoff
message_not_found	Invalid timestamp	Check message timestamp is correct

Retry Strategy

For rate limiting errors, implement exponential backoff:

1. Wait 1 second, retry
2. Wait 2 seconds, retry
3. Wait 4 seconds, retry
4. Wait 8 seconds, retry
5. Give up after 5 attempts

Rate Limits

Slack API rate limits:

• Tier 1: 1 request per second
• Tier 2: 20 requests per minute
• Tier 3: 50 requests per minute
• Tier 4: 100 requests per minute

Methods by tier:

• chat.postMessage: Tier 3 (50/min)
• conversations.list: Tier 2 (20/min)
• users.list: Tier 2 (20/min)
• files.upload: Tier 4 (100/min)

Related

• Slack API Documentation: https://api.slack.com/docs
• Block Kit Builder: https://app.slack.com/block-kit-builder
• Slack App Management: https://api.slack.com/apps