slack

This MCP server provides Slack integration tools built with Spring AI to interact with Slack channels. It supports sending messages to channels (with partial Markdown), querying channel history with paging support, uploading files either from a absolute path or via Base64 data, and scheduling messages to be sent at a future time. You can access these tools through the MCP server exposed by the Slack MCP module and configure authentication using a Slack bot token and target channel ID. Typical workflows include sending alerts or notifications, retrieving recent messages for audits, uploading resources or logs, and scheduling time-specific messages for reminders or status updates.

Prerequisites:

• Java 11+ and a JDK compatible with the project
• Gradle or the project’s build setup
• Access to Slack workspace with a Bot Token (xoxb- token) and a target channel

1. Build the project

./gradlew build

2. Locate the built JAR

• After a successful build, find the jar under build/libs (e.g., slack-mcp-server.jar).

3. Run the MCP server Option A: Run directly with the JAR and environment variables (example)

export SLACK_BOT_TOKEN=xoxb-your-bot-token
export SLACK_CHANNEL_ID=your-channel-id
java -Dfile.encoding=UTF-8 -jar path/to/slack-mcp-server.jar

Option B: If using Claude Desktop (as shown in the README)

• Create a claude_desktop_config.json with the following content:

{
  "mcpServers": {
    "slack-mcp": {
      "command": "java",
      "args": [
        "-Dfile.encoding=UTF-8",
        "-jar",
        "path/to/slack-mcp-server.jar"
      ],
      "env": {
        "SLACK_BOT_TOKEN": "xoxb-your-bot-token",
        "SLACK_CHANNEL_ID": "your-channel-id"
      }
    }
  }
}

• Replace the jar path and environment values accordingly, then launch via Claude Desktop.

Notes and tips:

• Ensure the Slack bot token has the necessary scopes (e.g., chat:write, channels:history, files:write) for the requested operations.
• For file uploads, absolute file paths are recommended to avoid path resolution issues; base64 uploads may consume more API tokens for large files.
• Slack API rate limits apply; implement paging when retrieving history to avoid hitting limits.
• When scheduling messages, specify the correct timezone and timestamp to ensure timely delivery.
• If you encounter jar signing or encoding issues, confirm Java version compatibility and rebuild with the appropriate JDK.
• Keep SLACK_CHANNEL_ID and SLACK_BOT_TOKEN secure; do not commit them to version control.