Blockworld

YouTube Video: https://youtu.be/EHHd7kv7y3I

A voxel world for an AI agent to build in.

• An MCP server — tools for placing blocks.

• A viewer — renders the world as line art, live, block by block as the agent works.

• Skills — markdown that teaches an agent what a fairytale castle or a dragon looks like, and how to build one here.

The agent brings the knowledge. The server gives it hands. The skills give it the brief.

Run it

npm install
npm run viewer        # → http://localhost:5173/viewer/

Opens with a mock castle so you can see it working straight away. Add ?live to suppress it.

Then point an agent at the MCP server:

{
  "mcpServers": {
    "blockworld": {
      "command": "node",
      "args": ["/absolute/path/to/blockworld/server.js"]
    }
  }
}

It broadcasts on a WebSocket, so the viewer shows each block as it lands.

> build me a castle
> build me a dragon

Related MCP server: Hayba

Controls

2 is the silhouette view — the best angle for judging what a build actually reads as.

Tools

Everything is cubes. place_sphere and place_tube don't render spheres or tubes — they rasterize a shape into cubes server-side. The point is tool-call economy: the agent describes a form (a path, a radius, a taper) instead of computing five thousand coordinates.

Skills

.claude/skills/
  blockworld/   scale, materials, primitives, build order   ← read first
  castle/       fairytale: slender spires, steep caps, gold
  dragon/       S-curve spine, membrane wings, taper

Plain markdown, no vendor syntax. Claude Code and Grok both discover .claude/skills/ automatically. Grok also reads .grok/skills/, and some agents use .agents/skills/ — the path doesn't matter to the content, so rename freely. Any other agent: point it at the files directly.

The one dial

config.js:

export const BLOCK_SIZE = 1.0;   // metres per block

Everything follows — viewer scale, server readouts, and the agent's own sense of how big to build. It doesn't read the block size from markdown; it calls world_info, which derives reference dimensions from the config at runtime:

One block is 50 cm.
  castle wall     18 tall
  castle tower    52 tall
  large dragon   100 long

The skills are written in ratios — wingspan = 1.5× body length, towers 3× the wall — never metres. So halving BLOCK_SIZE gets you a dragon that's still 50m long but made of 8× the cubes. No skill edits.

Layout

config.js            the one dial
palette.js           100 materials, shared
server.js            MCP over stdio + WebSocket :8080
viewer/index.html    Three.js from CDN, no build step
.claude/skills/      blockworld · castle · dragon