masseater/slack-webhook-mcp

Slack Webhook MCP Server

A Model Context Protocol (MCP) server that enables LLM applications like Claude Desktop to send messages to Slack channels via incoming webhooks.

Features

• Send plain text or markdown-formatted messages to Slack
• Simple and secure webhook URL management
• Built with Deno for modern TypeScript development
• Full test coverage

Installation

Prerequisites

• Deno installed on your system
• A Slack workspace with incoming webhooks enabled
• Claude Desktop (or another MCP-compatible client)

Setup

1. Clone this repository:

   git clone https://github.com/yourusername/slack-webhook-mcp.git
   cd slack-webhook-mcp
   

2. Create a Slack incoming webhook:

   • Go to your Slack workspace's App Directory
   • Search for "Incoming WebHooks" and add it
   • Choose a channel and create a webhook URL
   • Copy the webhook URL (it should look like https://hooks.slack.com/services/T00000000/B00000000/XXXXXXXXXXXXXXXXXXXXXXXX)

3. Configure your environment:

   cp .env.example .env
   # Edit .env and add your webhook URL
   

Configuration

Claude Desktop

Add this server to your Claude Desktop configuration file: ~/Library/Application Support/Claude/claude_desktop_config.json

{
  "mcpServers": {
    "slack-webhook": {
      "command": "deno",
      "args": ["run", "--allow-net", "--allow-env", "--allow-read", "/path/to/slack-webhook-mcp/src/index.ts"],
      "env": {
        "SLACK_WEBHOOK_URL": "https://hooks.slack.com/services/YOUR/WEBHOOK/URL"
      }
    }
  }
}

Using Compiled Binary

You can also compile the server to a standalone executable:

deno task build

Then use the binary in your configuration:

{
  "mcpServers": {
    "slack-webhook": {
      "command": "/path/to/slack-webhook-mcp/slack-webhook-server",
      "env": {
        "SLACK_WEBHOOK_URL": "https://hooks.slack.com/services/YOUR/WEBHOOK/URL"
      }
    }
  }
}

Usage

Once configured, you can use the following tool in Claude Desktop:

send_slack_message

Send a message to your configured Slack channel.

Parameters:

• message (required): The message text to send
• webhook_url (optional): Override the default webhook URL
• format (optional): Message format - "text" or "markdown" (default: "markdown")

Examples:

• "Send a Slack message saying the deployment was successful"
• "Notify the team on Slack that the tests are passing"
• "Send 'Build failed: timeout in test suite' to Slack with plain text format"

Development

Available Commands

# Run in development mode with auto-reload
deno task dev

# Run tests
deno task test

# Run tests with coverage
deno task test:coverage

# Type checking
deno task check

# Linting
deno task lint

# Format code
deno task fmt

# Build standalone executable
deno task build

Project Structure

slack-webhook-mcp/
├── src/
│   ├── index.ts                # Entry point
│   ├── server.ts               # MCP server implementation
│   ├── tools/
│   │   ├── slack_webhook.ts    # Slack webhook tool
│   │   └── slack_webhook_test.ts # Tool tests
│   ├── types.ts                # TypeScript types
│   └── index_test.ts           # Integration tests
├── deno.json                   # Deno configuration
├── README.md                   # This file
└── .env.example                # Environment variables example

Security

• Never commit your .env file or webhook URLs to version control
• Webhook URLs are validated to ensure they match Slack's format
• All errors are handled gracefully without exposing sensitive information

Contributing

1. Fork the repository
2. Create your feature branch (git checkout -b feature/amazing-feature)
3. Run tests and ensure they pass (deno task test)
4. Commit your changes (git commit -m 'Add amazing feature')
5. Push to the branch (git push origin feature/amazing-feature)
6. Open a Pull Request

License

This project is licensed under the MIT License - see the LICENSE file for details.

Acknowledgments

• Built using the Model Context Protocol SDK
• Powered by Deno
• Integrates with Slack Incoming Webhooks