slack

This MCP server provides a Slack integration that can operate over multiple transports (Stdio, SSE, and HTTP) and can route outgoing requests through a proxy if needed. It supports Slack workspace interactions including direct messages, group DMs, channels, and threads, with capabilities such as smart history fetch, message search, and embedded user information. By default, the server runs in a safe mode where the tool to post messages (conversations_add_message) is disabled; you can enable it via an environment variable if you need to post messages to channels or DMs. The tooling set includes conversations_history for retrieving messages, conversations_replies for thread histories, conversations_search_messages for flexible looking, and conversations_add_message for posting (when enabled). The server exposes these tools through the MCP interface and can be consumed by clients via Stdio, SSE, or HTTP transports depending on your setup.

Prerequisites:

• Node.js and npm (or npx) installed on your machine
• Access to the internet to fetch the MCP server package

Option A – Run with npx (recommended):

1. Ensure you have npx available: npm i -g npm
2. Run the MCP Slack server via npx: npx -y slack-mcp-server

Option B – Install locally with npm:

1. Initialize a project (if needed): mkdir my-slack-mcp && cd my-slack-mcp npm init -y
2. Install the Slack MCP server package: npm install slack-mcp-server
3. Run the server (adjust the path if necessary): npx slack-mcp-server

Notes:

• You can customize environment variables as described in the documentation (e.g., enable add_message with SLACK_MCP_ADD_MESSAGE_TOOL).
• If you plan to deploy behind a proxy or in OAuth/stealth modes, ensure your environment is configured accordingly.

Tips and common issues:

• If you enable conversations_add_message, provide a restricted list of channel_ids to limit posting risks or leave it unset to allow posting everywhere.
• When using SSE/HTTP transports, ensure your MCP client supports the chosen transport and tokens/scopes align with Slack permissions.
• The server caches user and channel information to speed up responses; if you notice stale data, consider refreshing cache by restarting the server.
• Review your Slack app permissions and OAuth mode vs stealth mode to match your deployment needs.
• For debugging, start the server with verbose logging if available in your version of the package, and verify that environment variables are picked up by the process.