mcp-notify

Minimal MCP server for sending Slack messages. Supports both bot tokens (xoxb) and user tokens (xoxc + cookie auth). Fire-and-forget — single send_message tool, nothing else.

Looking for a full-featured Slack MCP? Check out korotovsky/slack-mcp-server — it supports reading, searching, reactions, threads, DMs, and much more. We recommend it for most use cases.

This project exists because we needed two things it doesn't offer:

• Bot signature — in user-token mode, every message gets a :robot_face: context block so it's clear the message was sent by an AI assistant, not a human. In bot-token mode, the app name/icon already serves this purpose.
• Concurrent safety — SQLite with WAL mode and check-lock-recheck sync pattern, safe for multiple MCP instances running in parallel

Installation

Claude Code

Add to your MCP config (~/.claude.json globally or .mcp.json per project).

Bot token (recommended for Slack apps):

{
  "mcpServers": {
    "mcp-notify": {
      "type": "stdio",
      "command": "npx",
      "args": ["-y", "@pilat/mcp-notify"],
      "env": {
        "SLACK_MCP_BOT_TOKEN": "xoxb-..."
      }
    }
  }
}

User token (xoxc + cookie):

{
  "mcpServers": {
    "mcp-notify": {
      "type": "stdio",
      "command": "npx",
      "args": ["-y", "@pilat/mcp-notify"],
      "env": {
        "SLACK_MCP_XOXC_TOKEN": "xoxc-...",
        "SLACK_MCP_XOXD_TOKEN": "xoxd-..."
      }
    }
  }
}

Other MCP clients

Use npx @pilat/mcp-notify as the command with stdio transport. Pass credentials as environment variables:

# Bot token
SLACK_MCP_BOT_TOKEN=xoxb-... npx @pilat/mcp-notify

# User token
SLACK_MCP_XOXC_TOKEN=xoxc-... SLACK_MCP_XOXD_TOKEN=xoxd-... npx @pilat/mcp-notify

Environment Variables

Variable	Required	Description
SLACK_MCP_BOT_TOKEN	One of bot/user	Bot token (xoxb-...) from your Slack app
SLACK_MCP_XOXC_TOKEN	One of bot/user	User's xoxc-... token
SLACK_MCP_XOXD_TOKEN	With xoxc	User's xoxd-... session token (value of the d cookie)
SLACK_MCP_DATA_DIR	No	Custom path for SQLite cache (default: ~/.local/share/mcp-notify)

Set either SLACK_MCP_BOT_TOKEN or SLACK_MCP_XOXC_TOKEN + SLACK_MCP_XOXD_TOKEN. Setting both bot and user tokens is an error.

Bot token setup

1. Create a Slack app at api.slack.com/apps
2. Add the following OAuth scopes: channels:read, groups:read, users:read, usergroups:read, chat:write
3. Install the app to your workspace
4. Copy the Bot User OAuth Token (xoxb-...)

User token setup (xoxc + cookie)

1. Open Slack in browser (not desktop app)
2. Open DevTools → Network tab
3. Make any action in Slack (switch channel, send message)
4. Find any request to api.slack.com → Headers tab
5. SLACK_MCP_XOXC_TOKEN: from request payload, find token=xoxc-...
6. SLACK_MCP_XOXD_TOKEN: from Cookie header, find d=xoxd-... — copy only the xoxd-... part (without d=)

Architecture

Single tool: send_message. In user-token mode, messages include a :robot_face: context block. In bot-token mode, messages are sent without the signature (the app name/icon already identifies the sender). Both modes use Block Kit with plain text fallback.

• SQLite cache (~/.local/share/mcp-notify/data.db, WAL mode) — channels, users, user groups with lazy sync on first cache miss, 24h TTL
• Mention resolution — @username → <@U123>, @grouphandle → <!subteam^ID>. Groups take priority. Resolved in parallel.
• Concurrent sync safety — CAS-based check-lock-recheck pattern via sync_meta table