Fantasy World MCP Simulator

A Model Context Protocol (MCP) server for procedural fantasy world generation and evolution simulation. Starting from a simple event (like "a small cave"), it simulates anthropological and geographical changes over centuries, generating rich history, dungeons, cities, and events for fantasy settings.

Features

• Procedural History Generation: Simulate centuries of world evolution from simple starting conditions

• Anthropological Simulation: Population growth, technology progression, social organization evolution

• Geographical Changes: Resource dynamics, natural events, terrain modifications

• Location Evolution: Cave → Settlement → Village → City → Ruins progression

• Monster System: Dragons, giants, orcs, goblins, undead with raid mechanics, counter-attacks, extinction

• Quest Generation: Auto-generated quests for monster hunts, famine, disease, resource shortages

• Craft/Heritage System: Magical items, weapons, artifacts with rarities and hidden/lost heritage

• Religion & Belief System: Pantheons, monotheism, animism, cults with faith-based defense, religious quests, holy items

• Causal Event Tracking: Every event links back to its causes

• Multiple Export Formats: JSON, Markdown, narrative, GM notes with adventure hooks

• World Persistence: Load/restore worlds from saved JSON data (loadWorld tool)

Related MCP server: rpg-mcp

Installation

# Clone or navigate to the project
cd fantasy-world-mcp

# Install dependencies
npm install

# Build the project
npm run build

Configuration

Opencode Setup

Step 1: Build the project:

npm run build

Step 2: Add the MCP server to your opencode config (~/.config/opencode/opencode.json):

Add this to the "mcp" section of your config:

"mcp": {
    "world-evolution": {
        "type": "local",
        "command": ["node", "/path/to/fantasy-world-mcp/dist/index.js"]
    }
}

Step 3: Verify it's working:

opencode mcp list

You should see:

✓ world-evolution connected
  node /path/to/fantasy-world-mcp/dist/index.js

Important: The resources parameter must be explicitly set (even to an empty object {}) when initializing a world, otherwise the API will fail.

Step 4: Start opencode and ask your AI to create a world!

VS Code / Cursor Setup

Add to your MCP client configuration:

{
  "mcpServers": {
    "world-evolution": {
      "command": "node",
      "args": ["/path/to/fantasy-world-mcp/dist/index.js"],
      "cwd": "/path/to/fantasy-world-mcp"
    }
  }
}

Alternative: npx (no installation)

{
  "mcpServers": {
    "world-evolution": {
      "command": "npx",
      "args": ["-y", "tsx", "/path/to/fantasy-world-mcp/src/index.ts"]
    }
  }
}

Usage Guide for AI

1. Initialize a New World

Start by creating a world with initial conditions:

Tool: initializeWorld
Arguments:
{
  "event": "A small cave discovered by 20 refugees fleeing a great war",
  "locationType": "cave",
  "region": "mountains",
  "climate": "temperate",
  "resources": {
    "iron": 60,
    "stone": 80,
    "food": 40,
    "water": 70
  },
  "population": {
    "name": "The Exiles",
    "size": 20,
    "culture": "Mountain Folk",
    "organization": "tribal"
  }
}

Parameter Guide:

• event: Free-text description of the starting event

• locationType: cave, settlement, city, dungeon, fortress, temple, village, trade_post, ruins, landmark

• region: plains, mountains, forest, desert, swamp, hills, coastal, tundra, jungle

• climate: arctic, temperate, tropical, arid, continental

• resources: Object with resource names (iron, gold, silver, copper, wood, stone, food, water, magic, gems) and values 0-100

• population.name: Name of the starting group

• population.size: Initial population count

• population.culture: Cultural identity

• population.organization: nomadic, tribal, feudal, kingdom, empire

2. Run Simulation

Simulate history forward in time:

Tool: simulate
Arguments:
{
  "worldId": "<returned from initializeWorld>",
  "timespan": 500,
  "stepSize": 10,
  "complexity": "moderate",
  "enableConflict": true,
  "enableMigration": true,
  "enableTechProgress": true
}

Parameter Guide:

• timespan: Years to simulate (100-2000 recommended)

• stepSize: Years per simulation step (1-50, smaller = more detailed)

• complexity:

  • simple: Basic population and resource changes

  • moderate: + technology, migration, location evolution

  • complex: + conflict generation between populations

• enableConflict: Allow wars and disputes

• enableMigration: Allow population movement and new settlements

• enableTechProgress: Allow technological discoveries

3. Get Timeline

Retrieve the historical events:

Tool: getTimeline
Arguments:
{
  "worldId": "<world ID>",
  "startYear": 0,
  "endYear": 500
}

4. Get Current State

View the world's current state:

Tool: getWorldState
Arguments:
{
  "worldId": "<world ID>"
}

5. Generate Locations

Create specific locations like dungeons or cities:

Tool: generateLocation
Arguments:
{
  "worldId": "<world ID>",
  "locationType": "dungeon",
  "name": "Dark Keep",
  "description": "An ancient fortress abandoned after the great war"
}

Location Types: dungeon, city, village, fortress, temple, landmark

6. Export World

Get the world in your preferred format:

Tool: exportWorld
Arguments:
{
  "worldId": "<world ID>",
  "format": "gm_notes",
  "includeTimeline": true,
  "includeLocations": true
}

Export Formats:

• json: Structured data for programmatic use

• markdown: Formatted documentation

• narrative: Story-style chronicle

• gm_notes: Game master reference with adventure hooks

6b. Export World to File (For Large Worlds)

When exporting worlds after long simulations (500+ years, 100+ events), the output may exceed token limits. Use file-based export instead:

Tool: exportWorldToFile
Arguments:
{
  "worldId": "<world ID>",
  "format": "gm_notes",
  "includeTimeline": true,
  "includeLocations": true,
  "filePath": "exports/myworld_1524.md"  // Optional, default: exports/{worldId}_{timestamp}.{format}
}

What it does:

• Writes the export to a file in the exports/ directory

• Auto-creates the directory if it doesn't exist

• Returns the file path and file size

• Avoids token limit issues with large worlds

Default file paths:

• exports/{worldId}_{timestamp}.md (markdown)

• exports/{worldId}_{timestamp}.json (JSON)

• exports/{worldId}_{timestamp}.narrative (narrative)

• exports/{worldId}_{timestamp}.gm_notes (GM notes)

Reading exported files:

Tool: readExportFile
Arguments:
{
  "filePath": "exports/myworld_1524.md",
  "startLine": 1,
  "endLine": 100  // Optional: read in chunks
}

Pagination options:

• startLine/endLine: Read specific line ranges (1-indexed)

• startByte/endByte: Read specific byte ranges

• Returns: content, totalLines, totalBytes, lineRange, byteRange, hasMore

Use case example:

1. exportWorldToFile({ worldId: "abc-123", format: "gm_notes" })
   → Returns: { filePath: "exports/abc-123_1524.gm_notes", size: 45000 }

2. readExportFile({ filePath: "exports/abc-123_1524.gm_notes", startLine: 1, endLine: 50 })
   → Returns first 50 lines + metadata (hasMore: true)

3. readExportFile({ filePath: "exports/abc-123_1524.gm_notes", startLine: 51, endLine: 100 })
   → Returns next 50 lines + metadata (hasMore: true)

4. Continue until hasMore: false

This allows you to export and read massive worlds (10k+ tokens) without hitting MCP response limits.

7. Add Population

Add new populations (including monsters) to an existing world:

Tool: addPopulation
Arguments:
{
  "worldId": "<world ID>",
  "name": "Orc Warband",
  "size": 50,
  "race": "monster",
  "culture": "Hill Dwellers",
  "organization": "tribal",
  "monsterType": "orc",
  "dangerLevel": 4,
  "behavior": "aggressive"
}

Use cases:

• Add orc tribes after creating a human city

• Introduce elves, dwarves, or other races mid-simulation

• Spawn monster threats at specific times

8. Create Crafts/Heritage

Create magical items, weapons, books, artifacts, and lost heritage:

Tool: createCraft
Arguments:
{
  "worldId": "<world ID>",
  "name": "Sword of the Dawn",
  "description": "A legendary blade forged in the first light of the new age",
  "category": "weapon",
  "rarity": "legendary",
  "requiredTechLevel": 6,
  "requiredResources": { "iron": 50, "magic": 30, "gems": 20 },
  "creatorPopulationId": "<population ID>",
  "location": "<location ID>",
  "isHidden": false,
  "effects": ["+3 damage", "glows in darkness", "burns undead"]
}

Categories: weapon, armor, tool, artifact, book, jewelry, structure, relic
Rarities: common, uncommon, rare, legendary, mythic

Hidden Heritage: Set isHidden: true to create lost items that become adventure hooks:

• "The legendary Sword of Dawn is lost. Ancient texts hint it may be hidden in an ancient battlefield."

• Players can discover these during adventures

8b. Religion & Belief System

The simulation includes a complete religion/belief system that affects gameplay:

Belief Types:

• Pantheon: Multiple gods with different domains (war, nature, healing, etc.)

• Monotheism: Single deity worship

• Animism: Nature spirits and ancestor veneration

• Philosophy: Secular moral codes

• Cult: Worship of powerful beings (often evil/chaotic)

• Folk: Local traditions and customs

Faith Mechanics:

• Defense Bonus: Populations with organized religion get +0.15 defense (war domain), holy sites give +0.10

• Religious Quests: Pilgrimages, temple restoration, heresy suppression, relic recovery

• Holy Items: Blessed weapons, sacred relics, religious artifacts (higher rarity)

• Religious Conflicts: Populations with incompatible beliefs can become hostile

• Temple Locations: Special locations with divine protection and healing properties

Example:

Population: "The Dwarven Clan"
Belief: "The Stone Father" (Monotheism, domains: fortress, war)
Defense Bonus: +0.15 (organized religion with war domain)
Holy Site: "Mountain Temple" (+0.10 defense when defending this location)

9. Quest System

The simulation automatically generates serious quests when populations face problems they cannot solve:

Auto-Generated Quest Types:

• Monster Hunts: When monster threat > population defense

• Disease Cures: Plagues sweeping through large kingdoms/empires

• Resource Recovery: Critical shortages (iron, magic, etc.)

• Religious Quests: Pilgrimages, temple restoration, heresy suppression, relic recovery

Quest Properties:

• Urgency: low, medium, high, critical

• Deadline: Year by which quest must be completed

• Heroes Needed: Number of heroes required (0 = open for players)

• Consequences: Clear failure/success outcomes

Example:

CRITICAL QUEST: "Cure the Blazing Fever"
- A terrible plague is sweeping through the kingdom
- Physicians are powerless
- Heroes must find a cure in ancient texts or distant lands
- Deadline: 20 years
- Failure: Kingdom decimated, cities become ghost towns
- Success: Kingdom survives, heroes honored for generations

Complete Quests:

Tool: completeQuest
Arguments:
{
  "worldId": "<world ID>",
  "questId": "<quest ID>",
  "success": true,
  "completionNotes": "The heroes traveled to the Mountain Temple and retrieved the Sacred Herb"
}

Quests appear in GM Notes exports and are prioritized by urgency. Critical quests are highlighted for immediate player attention.

10. Load/Restore Worlds

MCP servers are in-memory only. When the server restarts, worlds are lost. Use loadWorld to restore previously saved worlds:

Step 1: Save world data after creation/simulation:

// After getWorldState or exportWorld, the AI should store the full world JSON
const worldData = JSON.stringify(world);
// AI stores this in its conversation context

Step 2: After restart, load the world:

Tool: loadWorld
Arguments: {
  "worldData": "{\"id\":\"abc-123\",\"timestamp\":400,\"society\":{...},...}"
}

Step 3: Continue simulation:

Tool: simulate
Arguments: {
  "worldId": "abc-123",
  "timespan": 100
}

The AI automatically handles this - just say "resume my world" or "continue the simulation" and it will use loadWorld() with the saved data.

Example Workflow

Here's a complete example of generating a fantasy setting:

// 1. Create the world with humans
const world = await initializeWorld({
  event: "A city founded by refugees near a river",
  locationType: "city",
  region: "plains",
  climate: "temperate",
  resources: { food: 70, wood: 60, water: 80 },
  population: {
    name: "River's Edge",
    size: 5000,
    culture: "Riverfolk",
    organization: "feudal"
  }
});

// 2. Add orc threat (not available at creation)
await addPopulation({
  worldId: world.worldId,
  name: "Orc Warband",
  size: 50,
  race: "monster",
  culture: "Hill Dwellers",
  organization: "tribal",
  monsterType: "orc",
  dangerLevel: 4,
  behavior: "aggressive"
});

// 3. Simulate 100 years of conflict
const history = await simulate({
  worldId: world.worldId,
  timespan: 100,
  stepSize: 10,
  complexity: "complex"
});

// 4. Export for your campaign
const campaignNotes = await exportWorld({
  worldId: world.worldId,
  format: "gm_notes"
});

Key insight: Add monsters/populations with addPopulation() instead of trying to specify them at creation. This gives you control over timing and numbers.

AI-Generated Crafts Example

The AI can create creative items during simulation:

// After simulating 100 years, the AI might create:

// 1. A magical weapon
await createCraft({
  worldId: world.worldId,
  name: "Dragonbane",
  description: "A greatsword forged from dragon-forged steel, humming with ancient power",
  category: "weapon",
  rarity: "legendary",
  requiredTechLevel: 7,
  requiredResources: { iron: 80, magic: 50, gems: 30 },
  creatorPopulationId: "pop_123",
  effects: ["+5 damage vs dragons", "burns with blue flame"]
});

// 2. A lost book
await createCraft({
  worldId: world.worldId,
  name: "Tome of the First Kings",
  description: "Ancient scroll containing the lost history of the first civilization",
  category: "book",
  rarity: "mythic",
  requiredTechLevel: 5,
  creatorPopulationId: "pop_456",
  isHidden: true,  // Players must find it!
  effects: ["reveals hidden truths", "grants +2 to history checks"]
});

// 3. Defensive structure
await createCraft({
  worldId: world.worldId,
  name: "Iron Barricade of River's Edge",
  description: "Massive fortified wall reinforced with magical wards",
  category: "structure",
  rarity: "uncommon",
  requiredTechLevel: 4,
  requiredResources: { iron: 60, wood: 40, stone: 50 },
  creatorPopulationId: "pop_123",
  effects: ["+50% defense against raids"]
});

These crafts appear in GM Notes exports and generate adventure hooks like:

• "The legendary Tome of the First Kings is lost. Ancient texts hint it may be hidden in a forgotten tomb."

• "The Dragonbane sword has been discovered! Powerful factions will seek to claim it."

AI vs Script: Why Use an AI Interface?

The Advantage Over Traditional Generators

How Persistence Works

The AI stores world data in its own context, not in the MCP server:

1. Create world → MCP returns worldId + full world JSON

2. AI saves → Stores the JSON in its conversation history/context

3. MCP restarts → Server loses all worlds (in-memory only)

4. Resume work → AI calls loadWorld() with the saved JSON data

5. Continue → World is restored, simulation continues

Why this design?

• MCP servers are stateless between restarts (by design)

• AI context is the "database" - it remembers everything

• No file I/O, no database setup, no migration issues

• Worlds travel with the conversation

Concrete Examples

Script Approach (Traditional)

{ "monsterCount": 2, "timespan": 400, "enableConflict": true }

→ Same output every time with same seed. Limited to predefined options.

AI Approach (This System)

Example 1: Dramatic Tension

"Create a world where ancient dragons are waking up after 500 years 
 of dormancy, and the human kingdom doesn't know the threat yet"

→ AI adjusts monster behavior (dormant dragons), creates foreshadowing events, generates adventure hooks about "strange tremors" and "sheep disappearing"

Example 2: Iterative Refinement

"Actually, make the orc kingdom more aggressive and have them 
  raid the dwarven mines every 50 years"

→ AI modifies monster behavior, adjusts raid frequency, creates specific conflict events without re-running everything

Example 3: Contextual Export

"Export this as handouts for my players, hiding the dragon threat"

→ AI creates player-friendly version, omits DM-only information, formats as in-world documents

Example 4: Resuming After Restart

"Load my world from last session"

→ AI retrieves saved JSON from context, calls loadWorld(savedData), continues simulation where it left off

The MCP Server Pattern

This isn't just a generator—it's a simulation engine that:

1. Runs in-memory - Fast, no database overhead

2. AI manages persistence - World data lives in AI context

3. Load/Resume - loadWorld() restores any saved world

4. Integrates with workflow - opencode, VTTs, campaign tools

Without AI: You'd need to write code to tweak anything
With AI: You just ask, and it uses the tools

Simulation Rules

The engine simulates these anthropological and geographical processes:

Population Dynamics

• Growth based on food and water availability

• Decline during shortages or conflicts

• Organization evolution: nomadic → tribal → feudal → kingdom → empire

Technology Progression

Populations discover technologies through a dynamic progression system based on multiple factors:

Tech Progression Formula:

• Base chance: 5% per population per 10-year step

• Population size bonus: +0.1% per 100 people (max +5%)

• Organization bonus: tribal +0%, feudal +2%, kingdom +4%, empire +6%

• Critical quest bonus: +3% per active critical quest (max +9%)

• Problem overload penalty: -2% if >5 active critical quests

• Resource abundance bonus: +1% per abundant resource (value > 60)

• Relic/artifact bonus: +5% if population has legendary/mythic item

• Trade route bonus: +2% if population has active trade routes

• Maximum chance: 50%

Complete Tech Tree:

Tech Prerequisites:

• Technologies unlock in order by level

• Can't discover level N+1 technology without completing level N

• Each technology contributes to the population's technology level

Tech Milestones: When a population reaches a new tech level, a TECH_MILESTONE event is created in the timeline, marking significant societal advancement.

Tech Level Effects:

• Level 2+: Can spawn basic heroes (Warrior, Rogue)

• Level 3+: Can spawn specialized heroes (Ranger, Cleric)

• Level 4+: Can spawn elite heroes (Paladin, Barbarian)

• Level 5+: Can spawn rare heroes (Mage, Bard)

Relics and Tech: Populations with legendary or mythic crafts/artifacts receive a +5% bonus to tech progression, representing the knowledge and inspiration gained from powerful items.

Location Evolution

• Cave → Settlement (50 years, 30+ population, tech level 3)

• Settlement → Village (100 years, 100+ population, tech level 5)

• Village → City (200 years, 300+ population, kingdom organization)

• City → Ruins (conflict + 300 years, 20% chance per step)

Resource Dynamics

• Consumption based on population size

• Regeneration for non-renewable resources

• Critical shortages trigger events

Natural Events

• Earthquakes (mountains)

• Forest fires (forest)

• Droughts (plains)

• Floods (swamp)

Output Examples

Timeline Output

Age of Discovery (0-50): Key developments: Beginning
Age of Settlement (50-100): Key developments: Earthquake, Agriculture
Age of Expansion (100-200): Key developments: Pottery, Migration
Age of Kingdoms (200-300): Key developments: Iron Working, Village Founded
Age of Empires (300-500): Key developments: City Founded, Writing

Adventure Hooks (from GM Notes)

1. The iron mines are running dry. Adventurers must find new sources.
2. Strange magical phenomena are appearing near the Luminary Depths.
3. The war between Mountain Clan and River Tribes is escalating.
4. Ancient ruins have been disturbed. Something ancient has awakened.

Tips for AI Users

Using with Opencode

Important: The MCP server maintains state during a single opencode session. Keep track of the worldId returned from initializeWorld and use it in subsequent calls.

1. Start opencode with the configured MCP server

2. Create a world - The AI will automatically include resources: {}:

   "Create a fantasy world starting with a cave"

   With monsters:

   "Create a world with dwarves and humans, enable 2 monsters (a dragon and orcs), simulate 400 years"

   The AI should call:

   initializeWorld({
     event: "a mysterious cave in the mountains",
     locationType: "cave",
     region: "mountains",
     climate: "temperate",
     population: [
       {name: "Mountain Exiles", size: 25, race: "human", culture: "Highlanders", organization: "tribal"},
       {name: "Dragon Horde", size: 15, race: "monster", monsterType: "dragon", dangerLevel: 8, behavior: "aggressive"}
     ],
     resources: {},  // Required - can be empty
     enableMonsters: true,  // Enable monster spawning
     monsterCount: 1  // Number of auto-generated monsters
   })

3. Note the worldId - The response will include a world ID like 12bff51b-...

4. Simulate - Ask the AI to use that specific worldId:

   "Simulate world 12bff51b-... for 500 years"

5. Export - Get the final output:

   "Export world 12bff51b-... as GM notes"

Pro tip: Ask the AI to "remember the world ID" or "keep track of the world" to maintain context across multiple tool calls.

Monster System

The world can include monster populations that act as threats to civilizations:

• Monster Types: dragon, giant, orc, goblin, undead, beast, demon, aberration, fae

• Behaviors: aggressive (raids constantly), territorial (defends lair), nomadic (migrates), dormant (sleeps), hiding (lurks)

• Danger Level: 1-10 threat rating

• Automatic spawning: Set enableMonsters: true and monsterCount: 2 to auto-generate monsters

• Monster events: Raids, infestations, invasions, awakening from dormancy

• Adventure hooks: Monster threats automatically generate quest hooks in GM notes

Resuming Worlds After Restart

MCP servers are in-memory only. When opencode restarts, worlds are lost. But the AI can restore them:

Step 1: AI saves world data after creation/simulation:

AI stores in context:
{
  "myWorld": {
    "id": "abc-123",
    "timestamp": 400,
    "society": {...},
    "events": [...],
    ...
  }
}

Step 2: After restart, AI loads the world:

Tool: loadWorld
Arguments: {
  "worldData": "{\"id\":\"abc-123\",\"timestamp\":400,...}"
}

Step 3: Continue simulation:

Tool: simulate
Arguments: {
  "worldId": "abc-123",
  "timespan": 100
}

The AI automatically handles this - just say "resume my world" or "continue the simulation".

Using with OpenAI-Compatible API

If your opencode setup uses an external API:

1. Edit .env.local with your API settings:

   API_BASE_URL=https://your-api-endpoint.com/v1
   API_KEY=your-api-key
   API_MODEL=your-model-name

2. Configure opencode to use these env vars (check your opencode docs)

3. The MCP tools will still work - they run locally regardless of where the AI model comes from

4. Start Small: Begin with 200-300 years to see the system's behavior

5. Use Seeds: Pass a seed parameter for reproducible results

6. Check Resources: Low food/water creates dramatic conflict scenarios

7. High Magic: Set magic > 70 for supernatural events

8. Multiple Populations: Create separate worlds and merge concepts

9. Export Early: Save interesting worlds before continuing simulation

10. Iterate: Generate, review, adjust parameters, regenerate

Troubleshooting

No Events Generated

• Increase timespan or decrease stepSize

• Set complexity to "moderate" or "complex"

• Ensure population size is reasonable (10+)

Simulation Too Simple

• Use complexity: "complex"

• Enable all options: conflict, migration, techProgress

• Start with larger population (50+)

Export Format Issues

• Try different formats: json for data, markdown for reading

• Set includeTimeline: false for shorter output

Quick Start

# 1. Build the project
npm run build

# 2. Add to opencode config (see Configuration section above)

# 3. Verify:
opencode mcp list

# 4. Start opencode and ask your AI:
# "Create a fantasy world starting with a cave"

Development

# Build
npm run build

# Run tests
npm run test

# Start server directly
npm start

# Task Management
npm tasks                                    # List all development tasks
node scripts/transition.cjs <id> in_progress # Mark task as in progress
node scripts/complete.cjs <id> "message"     # Complete task and commit

Task System

This project uses a task-based workflow for development:

• Location: tasks/ directory (ignored by git)

• Format: Individual .task.json files for each task

• States: pending, in_progress, completed

• Workflow:

  1. Create task file

  2. npm run task:transition <id> in_progress

  3. Implement, test, commit

  4. npm run task:complete <id> "commit message"

See tasks/README.md for full documentation.

License

ISC