Blockbench MCP Plugin

What is Blockbench MCP Plugin?

Blockbench MCP is an open-source plugin that runs a Model Context Protocol server inside the Blockbench desktop app, so AI agents like Claude Code, VS Code or Cline can build, texture and animate low-poly 3D models through tool calls.

The repository by jasonjgardner is a community project, not part of Blockbench itself. It ships two servers: the desktop plugin, which drives the running editor over HTTP, and a headless stdio server that edits, validates, converts and renders .bbmodel files without Blockbench open.

How to use Blockbench MCP Plugin?

Prerequisites: the Blockbench desktop app for the plugin server, or Node.js with npm for the headless server. No API key is needed.

1. In Blockbench, open File > Plugins, click Load Plugin from URL and paste https://jasonjgardner.github.io/blockbench-mcp-plugin/mcp.js.
2. Check Settings > General > MCP Server Port and MCP Server Endpoint. The examples below use the default http://localhost:3000/bb-mcp.
3. Keep Blockbench open and connect your client.

For the headless Blockbench MCP server, replace /path/to/models with an absolute path. --root is required and limits file access to that directory.

Claude Code

# Desktop plugin (HTTP)
claude mcp add blockbench --transport http http://localhost:3000/bb-mcp

# Headless (stdio)
claude mcp add bbmodel --transport stdio -- npx -y github:jasonjgardner/blockbench-mcp-plugin --root /path/to/models

Claude Desktop

Claude Desktop reaches the HTTP plugin through mcp-remote. Add to claude_desktop_config.json:

{
  "mcpServers": {
    "blockbench": {
      "command": "npx",
      "args": ["-y", "mcp-remote", "http://localhost:3000/bb-mcp"]
    },
    "bbmodel": {
      "command": "npx",
      "args": ["-y", "github:jasonjgardner/blockbench-mcp-plugin", "--root", "/path/to/models"]
    }
  }
}

On Windows, use "command": "cmd" and prepend "/c", "npx" to args.

VS Code

In .vscode/mcp.json:

{
  "servers": {
    "blockbench": {
      "url": "http://localhost:3000/bb-mcp",
      "type": "http"
    }
  }
}

Codex

codex mcp add blockbench --url http://localhost:3000/bb-mcp

The README also documents Cline, Antigravity, OpenCode and Ollama (uvx ollmcp -u http://localhost:3000/bb-mcp).

Key features of Blockbench MCP Plugin

• MCP server embedded in the Blockbench desktop app, served over Streamable HTTP on a configurable port and endpoint
• Separate headless stdio server for .bbmodel files, so several agents can work in parallel while you keep using the editor
• Tools for cubes, meshes, textures, PBR materials, UVs, animations, cameras, export and project setup
• Headless validation of geometry and animations, plus export to Bedrock .geo.json, Java block/item models and modded entity classes
• Local-only by default: listens on 127.0.0.1/::1 and rejects non-loopback Origin or Host headers
• Other Blockbench plugins can register their own MCP tools through a global MCP_QUEUE
• Companion Agent Skills and a sample project with prompt examples

Blockbench MCP Plugin tools

The desktop plugin exposes tools grouped by editor area:

• Modeling: place_cube, modify_cube, place_mesh, extrude_mesh, subdivide_mesh, create_sphere, create_cylinder, loop_cut_mesh and knife_tool create and reshape geometry.
• Outliner and elements: add_group, list_outline, duplicate_element, rename_element and remove_element organize the model.
• Textures and materials: create_texture, apply_texture, list_textures, create_pbr_material and import_texture_set handle textures and PBR channels.
• Camera and screenshots: set_camera_angle, capture_screenshot and capture_app_screenshot let the agent look at its own work.
• Project and export: create_project, get_project_info, list_export_formats and export_model.
• Scripting: risky_eval runs arbitrary JavaScript in Blockbench and can be switched off in settings.

The headless server uses bbmodel_* tools such as bbmodel_create, bbmodel_edit, bbmodel_validate, bbmodel_render and bbmodel_export_bedrock_geometry, plus blockbench_launch to open the desktop app.

Use cases of Blockbench MCP Plugin

• Blocking out game assets from a description: "Create a low-poly treasure chest with a hinged lid and a 32x32 texture."
• Building Minecraft-style mobs and items, then exporting Bedrock geometry or Java block/item models.
• Rigging and animating: "Add a walk cycle to this model and check that no limbs detach."
• Batch-checking a folder of .bbmodel files for floating parts or broken symmetry with the headless server.
• Letting the agent screenshot the viewport and iterate on proportions until the model looks right.
• Generating PBR texture sets and assigning channels to an existing model.

Blockbench MCP Plugin vs alternatives

If you work in a full 3D suite rather than a low-poly editor, Blender MCP gives agents similar control over Blender. For engine-side work, Unity MCP and Godot MCP connect agents to those editors. Blockbench MCP is the better fit for Minecraft-style, voxel-like and Bedrock/Java content because its tools and exporters follow Blockbench's own formats.

Troubleshooting Blockbench MCP Plugin

• Client can't connect: Blockbench must be running with the plugin loaded, and the URL must match the port and endpoint in Settings > General. The default path is /bb-mcp.
• Client in WSL2, a VM or another machine: the server only listens on loopback by default. Set MCP Server Host to 0.0.0.0 or :: and reload the plugin, but only on a trusted network, because the server has no authentication.
• Windows client fails to launch npx: use "command": "cmd" with "/c", "npx" in front of the arguments.
• Headless edits don't show in Blockbench: Blockbench does not reload files changed on disk. Reopen the model, and don't edit the same file in both at once.
• Headless rendering fails: the render tools need Node 23.6 or newer and a GPU; other headless tools work without them.