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
`check_scene`	Start a scene - Normal, Altered, or Interrupted?
`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

Scene Check

When starting a new scene, roll d10 vs Chaos Factor:

Result	When	Meaning
Normal	Roll > Chaos	Scene proceeds as expected
Altered	Roll ≤ Chaos, even	Same scene with a twist
Interrupted	Roll ≤ Chaos, odd	Completely different scene

Higher Chaos = more likely to have scenes go sideways.

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

Fate 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. Scenes more likely Normal, "No" more likely.
Medium (4-6): Balanced. Default starting point is 5.
High (7-9): Chaotic, unpredictable. Scenes often Altered/Interrupted, "Yes" 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: "Start a new scene where I enter the tavern",
  tools: [{
    type: "mcp",
    server_label: "mythic",
    server_url: "YOUR_ENDPOINT_URL",
    require_approval: "never",
  }],
});

Direct Testing

# Check if scene proceeds normally
curl -X POST YOUR_ENDPOINT_URL \
  -H "Content-Type: application/json" \
  -d '{"jsonrpc":"2.0","id":1,"method":"tools/call","params":{"name":"check_scene","arguments":{}}}'

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

# Adjust chaos after a wild scene
curl -X POST YOUR_ENDPOINT_URL \
  -H "Content-Type: application/json" \
  -d '{"jsonrpc":"2.0","id":3,"method":"tools/call","params":{"name":"adjust_chaos","arguments":{"direction":"up"}}}'

Example Session

You: I want to start a scene entering the tavern to meet my contact.
AI: [checks scene] ✅ Scene Normal - Roll: 8 vs Chaos 5
    The scene proceeds as planned. You enter the tavern...

You: Is my contact already there? (likely)
AI: [rolls fate] 🎲 Yes - Roll: 23 vs threshold 75
    Yes, you spot them in a corner booth.

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

You: Next scene - I follow the contact to the secret meeting.
AI: [checks scene] 🔄 Scene Altered - Roll: 2 vs Chaos 4
    The scene happens, but something's different...
    Perhaps guards are patrolling, or the meeting location changed?

dcm31

mcp-mythic