D&D MCP Server

Instructions

Implementation Reference

• src/gamemaster_mcp/main.py:773-821 (handler)

  The complete implementation of the 'roll_dice' tool handler, including schema (input parameters with descriptions), registration via @mcp.tool decorator, and the full logic for parsing dice notation, rolling dice (with support for advantage/disadvantage), applying modifiers, and formatting the output.
  @mcp.tool def roll_dice( dice_notation: Annotated[str, Field(description="Dice notation (e.g., '1d20', '3d6+2')")], advantage: Annotated[bool, Field(description="Roll with advantage")] = False, disadvantage: Annotated[bool, Field(description="Roll with disadvantage")] = False, ) -> str: """Roll dice with D&D notation.""" dice_notation = dice_notation.lower().strip() # Parse dice notation (e.g., "1d20", "3d6+2", "2d8-1") pattern = r'(\d+)d(\d+)([+-]\d+)?' match = re.match(pattern, dice_notation) if not match: return f"Invalid dice notation: {dice_notation}" num_dice = int(match.group(1)) die_size = int(match.group(2)) modifier = int(match.group(3)) if match.group(3) else 0 # Roll dice if advantage or disadvantage: if num_dice != 1 or die_size != 20: return "Advantage/disadvantage only applies to single d20 rolls" roll1 = random.randint(1, 20) roll2 = random.randint(1, 20) if advantage: result = max(roll1, roll2) roll_text = f"Advantage: {roll1}, {roll2} (taking {result})" else: result = min(roll1, roll2) roll_text = f"Disadvantage: {roll1}, {roll2} (taking {result})" total = result + modifier modifier_text = f" {modifier:+d}" if modifier != 0 else "" return f"🎲 **{dice_notation}** {roll_text}{modifier_text} = **{total}**" else: rolls = [random.randint(1, die_size) for _ in range(num_dice)] roll_sum = sum(rolls) total = roll_sum + modifier rolls_text = ", ".join(map(str, rolls)) if num_dice > 1 else str(rolls[0]) modifier_text = f" {modifier:+d}" if modifier != 0 else "" return f"🎲 **{dice_notation}** [{rolls_text}]{modifier_text} = **{total}**"