Slack MCP Server

MCP server for Slack API integration with HTTP transport.

Authentication Methods

Option 1: Bot/User Token (Recommended)

Standard Slack API tokens. Requires a Slack app with appropriate scopes.

export SLACK_TOKEN=xoxb-your-bot-token
# or
export SLACK_TOKEN=xoxp-your-user-token

Option 2: Cookie-Based Auth (User Impersonation)

Uses browser session cookies to impersonate a logged-in user. Useful when:

• You don't have admin approval for a Slack app

• You need to act as a specific user

• You want to access private channels the user is a member of

Extracting Tokens from Chrome

1. Open Chrome DevTools on your Slack workspace:

   • Navigate to https://your-workspace.slack.com

   • Press F12 or right-click → "Inspect"

   • Go to the Application tab

2. Get the

   • In DevTools, go to Console tab

   • Paste and run:

     JSON.parse(localStorage.localConfig_v2).teams[Object.keys(JSON.parse(localStorage.localConfig_v2).teams)[0]].token

   • Copy the xoxc-... token

3. Get the

   • In DevTools, go to Application → Cookies → https://your-workspace.slack.com

   • Find the cookie named d

   • Copy the Value (starts with xoxd-...)

   • ⚠️ The value is URL-encoded — keep it as-is

4. Get workspace details:

   • Team ID: In Console, run:

     JSON.parse(localStorage.localConfig_v2).teams[Object.keys(JSON.parse(localStorage.localConfig_v2).teams)[0]].id

   • User ID: Run:

     JSON.parse(localStorage.localConfig_v2).teams[Object.keys(JSON.parse(localStorage.localConfig_v2).teams)[0]].user_id

   • Domain: Your Slack URL (e.g., your-workspace.slack.com)

5. Create your env file:

   cp cookie-tokens.env.example /path/to/secrets/cookie-tokens.env
   # Edit the file with your extracted values

Using the Cookie Client

A shell script is provided for quick API calls:

# Set up your tokens
source /path/to/secrets/cookie-tokens.env

# Test authentication
./scripts/slack-cookie-client.sh auth

# List channels
./scripts/slack-cookie-client.sh channels 20

# Get channel history
./scripts/slack-cookie-client.sh history C0123ABCDEF 10

# Send a message
./scripts/slack-cookie-client.sh send C0123ABCDEF "Hello from the script!"

# Search messages
./scripts/slack-cookie-client.sh search "keyword"

# List users
./scripts/slack-cookie-client.sh users 50

Token Expiration

Cookie tokens expire when:

• You log out of Slack in the browser

• You change your password

• Slack rotates session tokens (typically every few weeks)

When tokens expire, repeat the extraction process.

Setup (Standard Token)

1. Get a Slack token (Bot Token xoxb-... or User Token xoxp-...)

2. Configure environment:

export SLACK_TOKEN=xoxb-your-token

3. Run:

npm install
npm run start:http

Docker

docker build -t slack-mcp .
docker run -d -p 3929:3929 -e SLACK_TOKEN=xoxb-... slack-mcp

Endpoints

• GET /health - Health check

• GET /tools - List available tools

• POST /call - Call a tool

Available Tools

Example

# List channels
curl -X POST http://localhost:3929/call \
  -H "Content-Type: application/json" \
  -d '{"name": "slack_list_channels", "arguments": {}}'

# Post message
curl -X POST http://localhost:3929/call \
  -H "Content-Type: application/json" \
  -d '{"name": "slack_post_message", "arguments": {"channel": "C123", "text": "Hello!"}}'

Token Scopes Required

For Bot Token (xoxb-...):

• channels:read, channels:history

• chat:write

• users:read

• reactions:write

• search:read (for search)

For User Token (xoxp-...):

• Same as above, plus any additional scopes for your use case

For Cookie Auth:

• No scopes needed — inherits all permissions of the logged-in user