日本語版はこちら

BCDice MCP Server Wrapper

Overview

This is an MCP (Model Context Protocol) server wrapper for BCDice. BCDice is a popular tabletop role-playing game (TRPG) dice bot in Japan, supporting over 100 different game systems.

With this MCP server, LLMs can not only execute standard dice roll commands (1d100, 2d6, etc.), but also retrieve game system help messages, command syntax patterns, and execute game-specific resolution mechanics.

Features

• Supports all BCDice game systems (e.g., Call of Cthulhu, Emoklore TRPG, and many others).
• Retrieve system-specific dice commands and rules.
• Inspect regex patterns used for command parsing.
• Access full BCDice capabilities, from standard dice rolls to complex game-specific tables and custom user-defined tables.

Installation

Node.js and npm are required as prerequisites.

Using npx

Add the following configuration to your MCP-compatible client settings:

{
  "mcpServers": {
    "bcdice": {
      "command": "npx",
      "args": [
        "-y",
        "@camegone/bcdice-mcp"
      ]
    }
  }
}

Installing from Repository

Clone the repository or download and extract the ZIP file:

git clone https://github.com/camegone/BCDiceMCPWrapper.git

Then, add the following to your MCP client configuration file. Make sure to replace <YOUR_INSTALL_PATH> with the actual path where this repository is located.

{
  "mcpServers": {
    "bcdice": {
      "command": "node",
      "args": [
        "<YOUR_INSTALL_PATH>/BCDiceMCPWrapper/build/index.js"
      ]
    }
  }
}

Available Tools

This server provides the following tools:

1. rollDice

Executes a dice roll according to the rules of the specified game system. In addition to standard dice (1d100, 2d6+4, etc.), system-specific check commands (such as Call of Cthulhu's CC<=50) are fully supported.

• Arguments:
  • diceCommand (string, required): The dice command expression to execute (e.g., '1d100', '3d6', '2d6+4', 'CC<=50').
  • system (string, optional, default: 'DiceBot'): Target game system name (retrievable via getGameSystemsList, e.g., 'Cthulhu', 'Cthulhu7th', 'DiceBot').
• Returns:
  • Dice roll result text (success/failure judgment, individual dice rolls, etc.). Returns the system help message if the command is invalid.

2. getDescription

Retrieves the help message (available commands and resolution explanations) and command regular expression patterns for the specified game system.

• Arguments:
  • system (string, optional, default: 'DiceBot'): Game system name to get descriptions for.
• Returns:
  • System help message (command specifications and formats)
  • Regular expression patterns for command matching

3. getGameSystemsList

Retrieves a list of all game systems available in BCDice.

• Arguments: None
• Returns:
  • A metadata list (JSON format) containing system IDs, display names, etc.

4. rollUserDefinedTable

Rolls on a user-defined custom table defined in plain text format.

• Arguments:
  • tableText (string, required): Table definition text containing table title, dice expression, and mapped outcomes.

    Table Title
    1D6
    1:One
    2:Two
    3:Three
    4:Four
    5:Five
    6:Six

• Returns:
  • Result text from rolling on the custom table.

5. getDiceBotVersion

Retrieves the version of the underlying BCDice library.

• Arguments: None
• Returns:
  • BCDice version string (e.g., BCDice version: 4.10.0).

6. getMCPServerVersion

Retrieves the version of this MCP server.

• Arguments: None
• Returns:
  • MCP server version string (e.g., MCP server version: 1.0.1).

Example Usage (Chat Log)

User: I'd like to test the BCDice MCP server. Let's execute rolls step by step. The system is Call of Cthulhu 6th Edition.

AI: I have checked the command specifications for Call of Cthulhu 6th Edition in BCDice. The check command format is CC<=skill_value (using the 1% critical/fumble rules).

Shall we start with ability score generation, or would you like to test skill checks (CC) first? For instance, a STR check is rolled as CC<=STR. Let me know what you'd like to roll. For now, shall we do a test roll with 1d100, which is commonly used for Sanity checks?

User: Let's do a test roll of 1d100 first.

AI: The result of rolling 1d100 was 27.

Let's move on to the next step. As typical in CoC 6th Edition, would you like to roll ability scores (3d6, 2d6+6, etc.), skill checks (CC<=skill_value), or a SAN check next?

User: An enemy is attacking. Let's decide who gets targeted. The party has five members: Ichiro through Goro.

AI: The enemy's attack target was determined to be Goro.

Next, shall we proceed with Goro's Dodge check (e.g., CC<=DEX*5) or the damage roll?

User: Let's roll Dodge.

AI: Please tell me Goro's Dodge skill value (DEX × 5, or the modified value if developed). Once you share it, I will roll CC<=skill_value.

User: DEX is 9.

AI: Goro's Dodge check: 29 <= 45 -> Success. The attack was successfully dodged!

What would you like to do next? (Enemy's follow-up attack, damage roll, another check, etc.)

User: Next is Ichiro's turn. Rolling Fist. Skill value is 50, base damage is 1d3, and damage bonus is 1d4.

AI: Ichiro's Brawl check: 56 > 50 -> Failure. The punch swung through the air and missed.

What would you like to do next? (Enemy's turn, another character's action, etc.)

User: Let's stop here. That was a great test. Thank you!

AI: You're very welcome! The BCDice MCP server handled Call of Cthulhu 6th Edition checks and dice expressions smoothly. Feel free to reach out anytime you want to play again. Have a great session!