Mode: Cognitive/Prompt-Driven — No standalone utility script; use via agent context.

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

• Create a Slack App at https://api.slack.com/apps

• Navigate to "OAuth & Permissions"

• 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

• Install app to workspace

• 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\nDuration: 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\nService: API Gateway\nStatus: 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:

• Wait 1 second, retry

• Wait 2 seconds, retry

• Wait 4 seconds, retry

• Wait 8 seconds, retry

• 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

Memory Protocol (MANDATORY)

Before starting: Read .claude/context/memory/learnings.md

After completing:

• New pattern -> .claude/context/memory/learnings.md

• Issue found -> .claude/context/memory/issues.md

• Decision made -> .claude/context/memory/decisions.md

ASSUME INTERRUPTION: If it's not in memory, it didn't happen.