jnaskali/rpg-mcp

RPG MCP Server

A simple MCP (Model Context Protocol) server for playing RPGs with Large Language Models. It provides tools for dice rolling, success checks, and random event generation.

Features

• check_success(probability, critical_rate) - Determines success/failure with optional critical results
• roll_dice(expr) - Rolls dice using standard RPG notation (e.g., '1d6', '2d8+3')
• generate_event() - Generates random RPG events for plot twists and surprises
• list_tools() - Lists all available tools

Installation

Prerequisites

• Python 3
• uv - A fast Python package installer

Setup

1. Clone the repository:

git clone https://github.com/jnaskali/rpg-mcp.git
cd rpg-mcp

2. Install dependencies with uv:

uv sync

Configuration

Add the following to your MCP client's configuration file (e.g., mcp.json in Claude Desktop or other MCP-compatible clients):

{
  "mcpServers": {
    "rpg-mcp": {
      "command": "/usr/bin/uv",
      "args": [
        "run",
        "python",
        "app.py"
      ],
      "cwd": "/PATH_TO/rpg-mcp/"
    }
  }
}

Replace /PATH_TO/rpg-mcp/ with the actual path to your rpg-mcp directory.

Usage

Once configured, the LLM can call the tools to:

• Roll dice for attacks, damage, or skill checks
• Determine action outcomes with customizable success probabilities
• Generate random events to drive the narrative forward

Example Prompt

Include instructions in your prompt like:

"Call check_success whenever a player character attempts something with a chance of failure, and generate_event to generate a random event at the start of a new scene or when moving to a new location."

The event generation system is inspired by Mythic Game Master Emulator.

[!IMPORTANT]
Tool calling works best with models that support function calling, such as Claude, GPT-4, Mistral, Llama, or Qwen.

Examples

Test the server by asking the LLM to generate a random event. The unique format should make it clear whether the tool is working or if the LLM is hallucinating results.