Slack

Purpose

Provide Slack access for reading messages and posting notifications. Supports two access methods: MCP server (recommended) or direct API via bot token.

Quick Reference

Method 1: MCP Server (Recommended)

If a Slack MCP server is configured, use it directly - no setup required.

Method 2: Bot Token + API

bash

# Check if Slack env vars are configured
grep -E '^SLACK_(BOT_TOKEN|CHANNEL_ID)=' .env

# Fetch recent messages
source .env
curl -s -H "Authorization: Bearer $SLACK_BOT_TOKEN" \
  "https://slack.com/api/conversations.history?channel=$SLACK_CHANNEL_ID&limit=10" \
  | jq '.messages[] | {ts: .ts, text: .text}'

Access Methods

MCP Server (Recommended)

If a Slack MCP server is available, it handles authentication and provides tools like:

•slack_list_channels - List available channels
•slack_read_messages - Read messages from a channel
•slack_post_message - Post a message to a channel
•slack_search - Search messages

Check MCP server availability before falling back to direct API.

Direct API via Bot Token

For projects without MCP, use Slack's REST API with a bot token.

Prerequisites

Add to .env file:

bash

# Slack Bot Token (xoxb-...)
# Get from: Slack App > OAuth & Permissions > Bot User OAuth Token
SLACK_BOT_TOKEN=xoxb-your-token-here

# Default Channel ID
# Get from: Right-click channel > View channel details > Copy ID (at bottom)
SLACK_CHANNEL_ID=C0XXXXXXXX

# Optional: Additional channels
SLACK_ALERTS_CHANNEL_ID=C0XXXXXXXX
SLACK_NOTIFICATIONS_CHANNEL_ID=C0XXXXXXXX

Bot Token Scopes

The Slack bot needs these OAuth scopes:

•channels:history - Read messages from public channels
•channels:read - View basic channel info
•chat:write - Post messages
•files:write - Upload files (optional)

Reading Messages

Via MCP (if available)

code

Use slack_read_messages tool with channel parameter

Via API

bash

source .env

# Fetch recent messages
curl -s -H "Authorization: Bearer $SLACK_BOT_TOKEN" \
  "https://slack.com/api/conversations.history?channel=$SLACK_CHANNEL_ID&limit=10" \
  | jq -r '.messages[] | "\(.ts): \(.text)"'

# Fetch messages in time range (Unix timestamps)
OLDEST=$(date -u -v-1H "+%s")  # 1 hour ago (macOS)
curl -s -H "Authorization: Bearer $SLACK_BOT_TOKEN" \
  "https://slack.com/api/conversations.history?channel=$SLACK_CHANNEL_ID&oldest=$OLDEST" \
  | jq '.messages[]'

Manual (Fallback)

•Open Slack desktop or web app
•Navigate to the target channel
•Copy the message text
•Provide to Claude for analysis

Posting Messages

Via MCP (if available)

code

Use slack_post_message tool with channel and text parameters

Via API

bash

source .env

# Post simple message
curl -s -X POST -H "Authorization: Bearer $SLACK_BOT_TOKEN" \
  -H "Content-Type: application/json" \
  -d '{
    "channel": "'"$SLACK_CHANNEL_ID"'",
    "text": "Hello from the bot!",
    "unfurl_links": false
  }' \
  "https://slack.com/api/chat.postMessage"

# Post with formatting (Blocks)
curl -s -X POST -H "Authorization: Bearer $SLACK_BOT_TOKEN" \
  -H "Content-Type: application/json" \
  -d '{
    "channel": "'"$SLACK_CHANNEL_ID"'",
    "blocks": [
      {
        "type": "header",
        "text": {"type": "plain_text", "text": "Status Update"}
      },
      {
        "type": "section",
        "text": {"type": "mrkdwn", "text": "*Service:* my-service\n*Status:* Healthy"}
      }
    ]
  }' \
  "https://slack.com/api/chat.postMessage"

Message Format

Common alert/notification format:

code

[SEVERITY] service-name - Message
Time: timestamp

Severity levels:

•[ERROR] - Requires immediate attention
•[WARN] - Potential issue, monitor
•[INFO] - Informational, no action needed

Verifying Access

Check MCP Availability

Look for Slack-related MCP tools in the available tools list.

Check Bot Token

bash

# Verify env vars exist
grep -E '^SLACK_' .env

# Test authentication
source .env
curl -s -H "Authorization: Bearer $SLACK_BOT_TOKEN" \
  "https://slack.com/api/auth.test" | jq '.ok, .user, .team'

# Test channel access
curl -s -H "Authorization: Bearer $SLACK_BOT_TOKEN" \
  "https://slack.com/api/conversations.history?channel=$SLACK_CHANNEL_ID&limit=1" \
  | jq '.ok'

Common Issues

Issue	Solution
`invalid_auth`	Check SLACK_BOT_TOKEN is correct and not expired
`channel_not_found`	Use channel ID (C0XXX), not channel name
`not_in_channel`	Add bot to channel: `/invite @BotName`
`missing_scope`	Add required OAuth scopes and reinstall app

Configuration

Config Location

Config path depends on how the plugin was installed:

Plugin Scope	Config File	Git
project	`.claude/skills/slack.yaml`	Committed (shared)
local	`.claude/skills/slack.local.yaml`	Ignored (personal)
user	`.claude/skills/slack.local.yaml`	Ignored (personal)

Precedence when reading (first found wins):

•.claude/skills/slack.local.yaml
•.claude/skills/slack.yaml
•Skill defaults