What is blockworld?

Blockworld is a voxel building world made for AI agents to build in, rather than for a human player to control directly. It gives an AI agent a set of tools to place cube-shaped blocks, and a live viewer that shows the world being constructed piece by piece as the agent works, drawn as simple line art. The project has three parts. An MCP server gives the agent tools such as placing boxes, cylinders, cones, spheres, and tubes, mirroring a shape to build the other half automatically, and removing blocks to carve out gates or windows. A browser-based viewer, built with Three.js and no separate build step, connects over a WebSocket and updates live as blocks land. A set of markdown skill files teaches the agent what things like a fairytale castle or a dragon should look like and how to build them using these tools, describing shapes as ratios rather than fixed sizes. The point of shapes like place_sphere or place_tube is efficiency: instead of the agent calculating thousands of individual block coordinates, it can describe a form, such as a curved path with a certain radius, and the server converts that into blocks on its own. Everything scales from one setting in a config file that defines how many meters a single block represents, and the skill files use proportions so a build stays correct in shape even if that scale changes. To try it, you install the dependencies with npm, run the viewer, and connect an agent such as Claude Code to the MCP server so it can start placing blocks, for example by asking it to build a castle or a dragon. The viewer includes keyboard and mouse controls for rotating, framing, and viewing the build from different angles, including a silhouette view for checking how a shape reads visually.