slack-mcp-server

The Slack MCP Server is a Model Context Protocol (MCP) server designed for Slack Workspaces. It supports multiple transport protocols (Stdio, SSE, and HTTP) and offers advanced features for interacting with Slack data through an AI agent or MCP client.

Key capabilities include:

• Stealth and OAuth Modes: Run in 'stealth mode' without requiring additional permissions or bot installations, or use OAuth tokens for secure access.
• Channel and Thread Interaction: Fetch messages from channels and threads using names (e.g., #general) or IDs.
• Smart History: Retrieve message history using pagination by date (e.g., d1, 7d, 1m) or by message count.
• Unread Messages: Efficiently retrieve unread messages with priority sorting (DMs > partner channels > internal) and support for marking messages as read.
• Search: Search messages across channels, threads, and DMs using filters like date, user, and content.
• Safe Message Posting: The conversations_add_message tool is disabled by default for safety and must be explicitly enabled.
• DM and Group DM Support: Full support for retrieving direct messages and group direct messages.
• Enterprise Support: Compatible with Enterprise Slack setups.
• Performance: Includes cache support for users and channels to speed up access.

Tools in the Slack MCP Server are controlled by two distinct layers: Registration and Runtime Permissions.

1. Registration (SLACK_MCP_ENABLED_TOOLS)

This determines which tools are visible to the MCP client.

• Usergroups tools are registered by default.
• Write tools (conversations_add_message, reactions_add, reactions_remove, attachment_get_data) are NOT registered by default to prevent accidental exposure. To enable them, you must either set their specific environment variable (e.g., SLACK_MCP_ADD_MESSAGE_TOOL) or explicitly list them in SLACK_MCP_ENABLED_TOOLS.

2. Runtime Permissions (Tool-specific env vars)

Even if a tool is registered, it may have channel restrictions.

• Using SLACK_MCP_ADD_MESSAGE_TOOL allows you to restrict message posting to specific channels (e.g., C123,C456) or use ! to exclude specific channels.

Behavior Matrix

# Example 1: Read-only mode (default)
{
  "env": {
    "SLACK_MCP_XOXP_TOKEN": "xoxp-..."
  }
}

# Example 2: Enable messaging to specific channels
{
  "env": {
    "SLACK_MCP_XOXP_TOKEN": "xoxp-...",
    "SLACK_MCP_ADD_MESSAGE_TOOL": "C123456789,C987654321"
  }
}

# Example 3: Enable messaging without channel restrictions
{
  "env": {
    "SLACK_MCP_XOXP_TOKEN": "xoxp-...",
    "SLACK_MCP_ENABLED_TOOLS": "conversations_history,conversations_add_message,reactions_add"
  }
}

To use a User OAuth token (SLACK_MCP_XOXP_TOKEN), you must create a Slack App at api.slack.com/apps and add the following scopes under OAuth & Permissions > User Token Scopes:

• channels:history / channels:read / channels:write
• groups:history / groups:read
• im:history / im:read / im:write
• mpim:history / mpim:read / mpim:write
• users:read
• chat:write
• search:read
• usergroups:read / usergroups:write

You can use the following App Manifest to preconfigure these permissions automatically.

{
    "display_information": {
        "name": "Slack MCP"
    },
    "oauth_config": {
        "scopes": {
            "user": [
                "channels:history",
                "channels:read",
                "groups:history",
                "groups:read",
                "im:history",
                "im:read",
                "im:write",
                "mpim:history",
                "mpim:read",
                "mpim:write",
                "users:read",
                "chat:write",
                "search:read",
                "usergroups:read",
                "usergroups:write",
                "channels:write"
            ]
        }
    },
    "settings": {
        "org_deploy_enabled": false,
        "socket_mode_enabled": false,
        "token_rotation_enabled": false
    }
}

To use the Slack MCP Server, you must provide authentication tokens via environment variables. You only need one of the following methods, with priority given in this order: xoxp (User OAuth) > xoxb (Bot Token) > xoxc/xoxd (Browser Session).

Option 1: Browser Session (Quickest, less secure)

Use this if you want to use your existing browser login. You need to provide two environment variables:

• SLACK_MCP_XOXC_TOKEN: Found via the browser console.
• SLACK_MCP_XOXD_TOKEN: Found via browser cookies.

Option 2: User OAuth Token (Recommended)

Provides full user permissions. Requires creating a Slack App and setting specific User Token Scopes.

• Environment Variable: SLACK_MCP_XOXP_TOKEN (starts with xoxp-).

Option 3: Bot Token

Provides bot-level permissions. Note that bots must be manually invited to channels to access them, and they cannot use the conversations_search_messages tool because they lack access to the search.messages API.

• Environment Variable: SLACK_MCP_XOXB_TOKEN (starts with xoxb-).

For Claude Desktop users, you can use the DXT extension to install the server without manual JSON editing.

1. Download the latest .dxt file from the releases page.
2. In Claude Desktop, go to Settings > Extensions.
3. Drag and drop the .dxt file into the window and click "Install".
4. Configure the following fields:
   • Authentication method: Choose xoxc/xoxd, xoxp, or xoxb.
   • Tokens: Provide the corresponding token (SLACK_MCP_XOXC_TOKEN/SLACK_MCP_XOXD_TOKEN for xoxc/xoxd, SLACK_MCP_XOXP_TOKEN for xoxp, or SLACK_MCP_XOXB_TOKEN for xoxb).
   • Add Message Tool: Enable this to allow posting messages.
   • User-Agent: Change this if using Enterprise Slack.
5. Enable the MCP Server.

IMPORTANT

If you encounter startup issues, you may need to disable the bundled node in Claude Desktop to use the node from your host machine (a known DXT bug).