Dice MCP

dice-mcp is a local Model Context Protocol (MCP) server for tabletop role-playing dice rolls. It uses Streamable HTTP at http://127.0.0.1:8000/mcp.

Run locally

This project uses uv. From the repository root, start the server with:

uv run dice-mcp

The server listens only on localhost. Leave it running while using it from an MCP host, then stop it with Ctrl+C.

Tool

roll_dice

Roll one or more dice and add a modifier.

Parameter	Type	Description
sides	integer	Number of sides on each die.
amount	integer	Number of dice to roll.
modifier	integer	Optional value added to the sum of the rolls; defaults to 0.
exploding	boolean	Optional; rerolls a die that reaches its maximum value. Defaults to false.

The result contains displayable individual rolls, their unmodified sum, the modifier, and the final total. An exploded die is marked with *; for example, an exploding d6 result might be {"rolls": ["6*", "3"], "sum": 9, "modifier": 2, "total": 11}.

Dice formulas

The dice utilities also parse conventional dice notation, ready for a formula-based MCP tool:

from dicemcp.dice import parse_formula, roll_formula

parse_formula("2d20+4")
roll_formula("6W6")

Both d/D and the German W/w separator are supported, as are modifiers such as d20-1. An omitted amount means one die.

Prompts

The server provides MCP prompts for common d20 tabletop workflows:

• ability_check
• saving_throw
• attack_roll (set advantage=true for a D&D attack roll that keeps the higher of 2d20)
• damage_roll
• advantage_roll (D&D advantage rolls 2d20 and keeps the higher die; set disadvantage=true to keep the lower die)

They instruct the model to call roll_dice and report the relevant dice and total. They are system-neutral guidance based on familiar d20 conventions.

Add it to LM Studio

Start the server in a terminal first:

uv run dice-mcp

Then, in LM Studio, open the Program tab, choose Install, then Edit mcp.json. Add this entry inside mcpServers:

{
  "dice-mcp": {
    "url": "http://127.0.0.1:8000/mcp"
  }
}

Save the configuration, enable the server in a chat, and ask a dice-related question such as: “Make a Dexterity check with a +3 modifier.” LM Studio supports local MCP servers from version 0.3.17 and uses Cursor-compatible mcp.json notation; see its MCP server guide for current setup details.