Unity MCP Light with a native Rust server. On Windows x86-64, macOS arm64/x86-64, and Linux x86-64, install MCPForUnity and click Start Server in HTTP Local mode. The package includes the Rust executable; no Python, Cargo, or terminal is required. See native setup and launch verification.

A slimmed-down fork of MCP for Unity that spends less of your AI's context window on tool definitions.

---

Based on upstream v10.3.0. This update keeps Light’s reduced tool set and adds the local Blender Bridge, Unity 6.6 compatibility fixes, improved test recovery after domain reloads, and Pi / Trae CN client support.

Why this fork

Every MCP tool a server exposes has a name, a description and a parameter schema, and many clients send all of them to the model before you type a word. The upstream MCP for Unity 10.3.0 ships 49 tools, about 30k tokens of definitions. That context is paid on every conversation, whether or not you ever touch ProBuilder or the Profiler.

This fork removes tools that most Unity workflows don't need and trims the definitions of the ones that remain:

	Upstream	Light
Tools	49	39
Tool definitions (approx. tokens)	~30.5k	~19.5k
Skill: SKILL.md, loaded when the skill triggers (approx. tokens)	~3.8k	~4.1k
Skill: reference docs, read on demand (approx. tokens)	~41.2k (4 files)	~34.3k (4 files)
Skill total (approx. tokens)	~45.0k	~38.5k

The skill drops the ProBuilder guide and every section about removed tools, and adds a short guide to inspect_prefab. Token counts are characters ÷ 4.

Everything else — scenes, GameObjects, components, scripts, assets, prefabs, materials, shaders, procedural textures, camera, graphics, physics, builds, tests, UI Toolkit, API reflection — works the same as upstream.

What was added

blender_bridge connects Unity directly to a running BlenderMCP addon. It inspects Blender objects, imports selections or scenes, captures screenshots, and provides addon diagnostics. It belongs to the optional asset_gen group and has settings on the Generative tab. Blender must already be running with its addon connected.

inspect_prefab: a read-only prefab inspector (about 460 tokens of definition) that answers in compact, indented text under a character budget instead of JSON. It never opens a Prefab Stage, marks anything dirty or saves.

Mode	Answers
tree	What is in this prefab? Hierarchy to depth 2 with short component names; identical siblings collapse (Wheel_FL..RR x4); nested prefabs, inactive objects and missing scripts are marked. root= and filter= narrow it.
node	What are this object's settings? Only fields that differ from a freshly added component, with references resolved to paths and UnityEvent listeners spelled out.
refs	What is wired to what? Every object reference and persistent listener, by object; asset links from built-in components grouped by asset.
overrides	What does this variant or nested prefab change? Base chain, old -> new values, added and removed components and objects.
usages	Which prefabs and scenes use script X or asset Y, including through nested prefabs?
problems	Missing scripts, references to deleted objects, broken nested prefab links, broken listeners and material/submesh mismatches, for a prefab or a folder.

The normal path is manage_prefabs get_info → inspect_prefab tree → node or refs.

Animation restored

manage_animation is available again in native Rust and the Python fallback: Animator control, controller states/transitions/layers/blend trees, AnimationClip curves/events and 15 presets. See the animation skill guide and restoration verification. HTTP clients enable the animation group; stdio enables it initially.

What was removed

Tool	What it did
generate_image, generate_model, generate_audio	AI asset generation through third-party providers
import_model	Sketchfab marketplace search and import
manage_probuilder	ProBuilder mesh modeling
manage_profiler	Profiler sessions, counters, memory snapshots, Frame Debugger
manage_vfx	VFX Graph, particles, line and trail renderers
manage_packages	Package Manager install/remove/search
unity_docs	Fetching docs from docs.unity3d.com
debug_request_context	Server debugging helper
manage_script_capabilities	Listed the supported script-edit operations

import_model_file (local .fbx/.obj/.glb/.gltf/.zip) is kept.

Each removed tool is gone from the Python server, the Unity handlers, the CLI, the tests and the bundled unity-mcp-skill docs, so nothing still describes a tool that no longer exists.

Other changes:

• Smaller schemas. Optional parameters no longer carry Pydantic's null padding. Optional[str] = None used to be advertised as {"anyOf": [{"type": "string"}, {"type": "null"}], "default": null} and is now just {"type": "string"}. That alone saves about 3.5k tokens. Explicit null arguments are still accepted.
• read_console returns errors only by default (it used to return errors, warnings and logs). Projects with many warnings no longer flood the context; pass types=["error", "warning"] when you want warnings.
• get_test_job now recommends a wait_timeout of 15–30 seconds instead of 30–60.

Install the Python fallback

Requirements: Unity 2021.3 LTS – 6.x, Python 3.10+ and uv. Works with any MCP client (Claude Code, Claude Desktop, Cursor, VS Code, Windsurf, Cline, Gemini CLI and others).

1. Add the Unity package. In Unity, open Window → Package Manager → + → Add package from git URL and enter:

   https://github.com/Noongits/unity-light-mcp-rust.git?path=/MCPForUnity#main
   

   The package keeps the upstream package id (com.coplaydev.unity-mcp), so remove the upstream package first if you have it installed.

2. Configure your client. Open Window → Unity MCP Light, and on the Connect tab choose Configure All Detected Clients (or configure one client), then restart your MCP client.

   Clients are registered under the server name unity-mcp-light (for example claude mcp add ... unity-mcp-light in Claude Code, [mcp_servers.unity-mcp-light] in Codex). The Python server is fetched from this repository's Server/ folder on main, not from PyPI, so you get this fork's trimmed tool set without extra setup.

3. Install the skill (optional). Install Skills on the Connect tab copies the agent skill to ~/.claude/skills/unity-mcp-light (Claude Code) or ~/.codex/skills/unity-mcp-light (Codex).

4. Try it. Ask: "Create a cube at the origin and add a Rigidbody."

To run the server from a local clone instead, set Advanced → Server Source to your clone's Server folder.

Keeping context small

• Tool groups. Tools are grouped (core, vfx, ui, testing, docs, scripting_ext, asset_gen). Only core is on by default over HTTP; turn the others on when you need them with manage_tools, or on the Tools tab in Unity. The vfx group now holds only manage_shader and manage_texture.
• Clients with tool search (such as Claude Code) load tool definitions only when needed, so the savings here matter most for clients that load every definition up front.
• The skill. unity-mcp-skill/ gives agents usage guidance. It is large; install it only if your agent benefits from it.

Development

The server lives in Server/, and the Unity package lives in MCPForUnity/.

cd Server
uv run --extra dev pytest -q

To measure how many tokens the tool definitions cost, list the tools through FastMCP and count the characters of each serialized definition (roughly 4 characters per token).

Credits

This is a fork of MCP for Unity by Coplay and its contributors. All the real work is theirs; this fork only trims it. For the full feature set, documentation and community, use the upstream project.

If MCP for Unity helped your research, please cite the original work:

@inproceedings{wu2025mcpunity,
  author    = {Wu, Shutong and Barnett, Justin P.},
  title     = {{MCP-Unity}: {Protocol-Driven} Framework for Interactive {3D} Authoring},
  year      = {2025},
  isbn      = {9798400721366},
  publisher = {Association for Computing Machinery},
  address   = {New York, NY, USA},
  url       = {https://doi.org/10.1145/3757376.3771417},
  doi       = {10.1145/3757376.3771417},
  series    = {SA Technical Communications '25}
}

Not affiliated with Unity Technologies.

License: MIT — see LICENSE.