D20

🇹🇷 Türkçe README için tıklayın / Click here for Turkish README

A powerful MCP (Model Context Protocol) server for dice rolling in RPG games. Built with FastMCP and the d20 library, this server brings comprehensive dice mechanics to Claude and other MCP clients.

Perfect for D&D, Pathfinder, and any tabletop RPG that uses standard dice notation!

✨ Features

• 🎯 Simple Rolls: Quick 1d20+5 expressions with instant results
• 📊 Detailed Analysis: See every die roll with AST breakdown
• ⚡ Batch Rolling: Roll multiple expressions efficiently
• ✅ Syntax Validation: Check expressions before rolling
• 🎮 Advanced Mechanics: Keep/drop, reroll, exploding dice, and more
• 🤖 LLM-Optimized: Comprehensive tool descriptions for AI understanding

🚀 Quick Start

Easy Setup (Remote MCP)

The quickest way to use d20-mcp - no installation needed!

1. Open Claude Desktop
2. Go to Settings → Connectors
3. Click Add Custom Connector
4. Enter the URL: https://d20-mcp.fastmcp.app/mcp

Note: Remote MCP support is currently in beta and available for Claude Pro, Max, Team, and Enterprise users.

Local Installation (Alternative)

For local installation with uvx:

uvx --from git+https://github.com/saidsurucu/d20-mcp d20-mcp

Claude Desktop Configuration (Local)

Add this to your claude_desktop_config.json:

macOS: ~/Library/Application Support/Claude/claude_desktop_config.json Windows: %APPDATA%\Claude\claude_desktop_config.json

{
  "mcpServers": {
    "d20-mcp": {
      "command": "uvx",
      "args": [
        "--from",
        "git+https://github.com/saidsurucu/d20-mcp",
        "d20-mcp"
      ]
    }
  }
}

Restart Claude Desktop completely (Quit and reopen), then look for the 🔨 hammer icon!

📸 Screenshot

🎮 Usage Examples

Once installed, try these prompts with Claude:

Basic Rolling

Roll 1d20+5 for my attack

Character Creation

Roll 6 sets of 4d6kh3 for ability scores

Combat

Roll attack (1d20+7) and damage (2d8+4) for my greatsword

With Advantage

Roll 2d20kh1+5 for my Perception check with advantage

Complex Expressions

Roll (1d4+1)*2 for Magic Missile damage

🛠️ Available Tools

roll

Quick dice rolls returning total and formatted result. Perfect for standard gameplay.

Use for: Attack rolls, ability checks, damage, saving throws

roll_detailed

Comprehensive breakdown with AST structure showing individual die values and operations.

Use for: Character creation, debugging complex rolls, transparency

roll_batch

Roll multiple different expressions in one operation.

Use for: Combat rounds, rolling all ability scores, party checks

validate_syntax

Validate expressions without rolling (no randomness).

Use for: Testing complex expressions, user input validation

📝 Supported Dice Notation

Basic

• 1d20 - Roll one 20-sided die
• 3d6 - Roll three 6-sided dice
• d20 - Equivalent to 1d20

Keep/Drop

• 4d6kh3 - Keep highest 3
• 4d6kl1 - Keep lowest 1
• 4d6p1 - Drop lowest 1

Reroll

• 1d20rr<10 - Reroll until ≥10
• 1d20ro1 - Reroll 1s once

Exploding Dice

• 1d6e - Explode on max
• 1d6e6 - Explode on 6

Min/Max

• 1d20mi10 - Minimum 10
• 1d20ma20 - Maximum 20

Arithmetic

• 1d20+5 - Addition
• 2d6-1 - Subtraction
• 3d6*2 - Multiplication
• (1d4+1)*2 - Parentheses

Advanced

• 2d20kh1+5 - Advantage in D&D
• 2d20kl1+2 - Disadvantage
• 8d6 [fire] - Annotated damage (with allow_comments)

🎯 Common RPG Use Cases

D&D 5e Character Creation

Roll me 6 ability scores using 4d6 keep highest 3

Attack with Advantage

I have advantage on this attack. Roll 2d20kh1+8

Critical Hit

I crit! Roll 4d6+2d6+5 for my sneak attack damage

Multiple Saves

Roll saves for 4 party members: 1d20+5, 1d20+2, 1d20+7, 1d20+3

🔧 Development

Local Testing

# Clone the repository
git clone https://github.com/saidsurucu/d20-mcp.git
cd d20-mcp

# Run with uv
uv run server.py

# Or with Python directly (after installing dependencies)
python server.py

Project Structure

d20-mcp/
├── server.py          # Main MCP server with 4 tools
├── pyproject.toml     # Project configuration
├── README.md          # English documentation
├── README.tr.md       # Turkish documentation
└── LICENSE            # MIT License

🤝 Contributing

Contributions are welcome! Feel free to:

• Report bugs
• Suggest new features
• Submit pull requests
• Improve documentation

📄 License

MIT License - see LICENSE file for details.

🙏 Credits

Built with:

• d20 - Powerful dice rolling engine
• FastMCP - FastMCP framework
• MCP - Model Context Protocol

📚 Learn More

• Model Context Protocol Documentation
• FastMCP Documentation
• d20 Library Documentation

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Made with ❤️ for the TTRPG community