Command-MCP

Command MCP

Expose your Minecraft server as an MCP (Model Context Protocol) server, so AI assistants such as Claude can operate your server remotely: search and run commands, use in-game Tab completion, and build datapacks — all through a standard MCP client.

Built for Fabric with zero additional dependencies: the MCP server uses Streamable HTTP transport (POST/GET/DELETE /mcp) with JSON-RPC 2.0, implemented on the JDK's built-in HttpServer and Minecraft's bundled Gson.

Features

• Command access — search registered commands (vanilla and mods), execute commands as console (OP level 4) on the server main thread with captured output, run read-only queries, and get Tab-completion suggestions that match in-game behavior.
• Datapack workflow — inspect server info (version, pack_format, directory layout), list datapacks, read/write/delete datapack files, and reload with full error reporting (.mcfunction syntax errors, JSON errors, incompatible pack_format).
• Session management — Mcp-Session-Id based sessions with idle timeout, SSE keepalive streams, and optional Authorization: Bearer token auth.
• In-game awareness — chat notifications when an AI client connects or disconnects.
• Safe defaults — binds to 127.0.0.1 only; datapack file writes can be disabled.

Requirements

• Minecraft 1.20.1
• Fabric Loader >= 0.19.3
• Fabric API
• Java >= 17

Getting Started

1. Drop the mod jar into your mods folder and start the game/server.
2. The MCP server starts automatically:
   • Dedicated servers: enabled by default.
   • Single-player / client: disabled by default; set enabled=true in the config to turn it on.
3. Point your MCP client at http://127.0.0.1:8123/mcp (Streamable HTTP).

Example Claude Desktop configuration:

{
  "mcpServers": {
    "minecraft": {
      "type": "http",
      "url": "http://127.0.0.1:8123/mcp",
      "headers": {
        "Authorization": "Bearer <your-token>"
      }
    }
  }
}

Configuration

Config file: config/command-mcp.properties (created with defaults on first launch).

MCP Tools

Security Notes

• The server executes commands at OP level 4 — treat MCP access as full server access.
• By default the server only listens on 127.0.0.1. If you expose it over a network, always set an authToken.
• Set datapackWrite=false to keep the datapack tools read-only.

Development

./gradlew build

The built jar lands in build/libs/.

License

Released under the GPL-3.0 license. If you use this code in your project, your project must also be open-sourced under a compatible license.