Mythic GME MCP Server

A Mythic Game Master Emulator implementation as an MCP server. Perfect for solo RPGs or GM-less sessions.

Tools

Tool	Description
`roll_fate`	Ask a yes/no question with given odds
`get_chaos`	Get current Chaos Factor (1-9)
`set_chaos`	Set Chaos Factor to specific value
`adjust_chaos`	Increment or decrement Chaos Factor

How It Works

The Fate Chart

Ask the oracle a yes/no question and set the odds:

Odds	When to use
`impossible`	It would break reality
`no_way`	Extremely unlikely
`very_unlikely`	Really doesn't fit
`unlikely`	Probably not
`50_50`	Could go either way
`somewhat_likely`	Leans toward yes
`likely`	Probably yes
`very_likely`	Almost certainly
`near_sure_thing`	Only extreme circumstances prevent it
`sure_thing`	Would be shocking if no
`has_to_be`	Practically certain

Results

Yes / No - Standard answers
Exceptional Yes - Yes, and even better than expected
Exceptional No - No, and things get worse
Random Event - On doubles (11, 22, 33...) something unexpected happens!

Chaos Factor

The Chaos Factor (1-9) represents how out of control the story is:

Low (1-3): Stable, predictable. "No" answers more likely.
Medium (4-6): Balanced. Default starting point is 5.
High (7-9): Chaotic, unpredictable. "Yes" answers more likely.

After each scene:

Scene went as expected → decrease chaos
Scene spiraled out of control → increase chaos

Usage

With OpenAI Responses API

const response = await openai.responses.create({
  model: "gpt-4o",
  input: "Does the guard notice me sneaking past? (unlikely)",
  tools: [{
    type: "mcp",
    server_label: "mythic",
    server_url: "https://dcm31--fa6708b4eddd11f0ba2d42dde27851f2.web.val.run",
    require_approval: "never",
  }],
});

Direct Testing

# Check chaos factor
curl -X POST https://dcm31--fa6708b4eddd11f0ba2d42dde27851f2.web.val.run \
  -H "Content-Type: application/json" \
  -d '{"jsonrpc":"2.0","id":1,"method":"tools/call","params":{"name":"get_chaos","arguments":{}}}'

# Roll fate
curl -X POST https://dcm31--fa6708b4eddd11f0ba2d42dde27851f2.web.val.run \
  -H "Content-Type: application/json" \
  -d '{"jsonrpc":"2.0","id":2,"method":"tools/call","params":{"name":"roll_fate","arguments":{"odds":"likely"}}}'

# Increase chaos after a wild scene
curl -X POST https://dcm31--fa6708b4eddd11f0ba2d42dde27851f2.web.val.run \
  -H "Content-Type: application/json" \
  -d '{"jsonrpc":"2.0","id":3,"method":"tools/call","params":{"name":"adjust_chaos","arguments":{"direction":"up"}}}'

Example Session

You: Does the tavern have a back exit? (likely)
AI: [rolls fate] 🎲 Yes - Roll: 23 vs threshold 75

You: Is anyone watching it? (50/50)  
AI: [rolls fate] 🎲 Exceptional No - Roll: 98 vs threshold 45
    The exit is completely unguarded and hidden behind barrels.

You: That scene went smoothly, decrease chaos
AI: [adjusts chaos] 📉 Chaos Factor decreased: 5 → 4

dcm31

mcp-mythic