Mirven

Add the package, and your editor serves MCP at http://127.0.0.1:8765/mcp. Point Claude Code, Cursor, VS Code, Codex or any other MCP client at it. The agent can then compile your code and read the errors, build and change scenes, look at screenshots of what it made, and run your tests.

There is no Python server, no Node process, no uv, no bridge to keep alive. The server is a few C# files in an editor assembly, and it starts when Unity starts.

Install

Package Manager → + → Add package from git URL, then paste:

https://github.com/siiplasplas/unity-mcp.git

Or add it to Packages/manifest.json, pinned to a release:

"com.mirven.unity-mcp": "https://github.com/siiplasplas/unity-mcp.git#v0.1.0"

When Unity finishes importing, the server is running. Window → Unity MCP shows its status, the URL and the calls it has handled.

Connect your agent

Claude Code

claude mcp add --transport http unity http://127.0.0.1:8765/mcp

Cursor, in .cursor/mcp.json

{ "mcpServers": { "unity": { "url": "http://127.0.0.1:8765/mcp" } } }

VS Code, in .vscode/mcp.json

{ "servers": { "unity": { "type": "http", "url": "http://127.0.0.1:8765/mcp" } } }

Codex, in ~/.codex/config.toml

[mcp_servers.unity]
url = "http://127.0.0.1:8765/mcp"

Claude Desktop, which only speaks stdio, through mcp-remote

{ "mcpServers": { "unity": { "command": "npx", "args": ["mcp-remote", "http://127.0.0.1:8765/mcp"] } } }

The Unity MCP window has all of these with a copy button, already filled in with your port.

What the agent sees

The island at the top was built in an empty scene by 55 tool calls: materials, primitives, a point light, a parented cottage and a boat. tools~/demo.py replays them, so you can build it yourself.

Screenshots come back as images, not file paths. A model that can see can check its own work: whether the roof sits on the walls, whether the camera frames the object, whether the light is on.

The loop: edit, compile, test, fix

compile waits for Unity to finish and returns the errors with file, line and column. run_tests waits for the Test Runner and returns each failure's message and the line it came from. Here is the output of one session, unedited:

Tools

21 tools. Every tool that changes the project is a single Undo step, so you can take back anything the agent did with Ctrl+Z, or ask it to call undo.

Area	Tool	What it does
Editor	editor_state	Unity version, project, render pipeline, play and compile state, open scenes, selection, console counts
	compile	Import changed files, compile, wait, and return errors and warnings with file(line,col)
	console	Recent Console entries, errors and warnings by default
	play	Enter, exit, pause, resume or step play mode
	menu	Run any menu item by path
	undo	Undo or redo the last changes
	select	Select objects or assets and frame them, so you see what the agent means
Scene	hierarchy	Compact tree of the open scenes, or of one object
	scene	List, open, save, create or save-as. Refuses to drop unsaved changes unless asked
	inspect	Transform and every component's serialized properties, with paths for set_property
	create_object	Primitive, empty or prefab instance, with transform, components and material in one call
	modify_object	Name, parent, transform, active, tag, layer, static flag, on one or many objects
	delete_object	Delete objects and their children
	add_component	Add a built-in component or your own script, and set its fields
	remove_component	Remove a component
	set_property	Set serialized properties on components, materials or ScriptableObjects. References take asset or scene paths
	save_prefab	Save a scene object as a prefab and connect it
Assets	find_assets	Search like the Project window: t:Material red, l:Enemy

Writing scripts is left to the agent's own file tools, which every client already has and which are better at it. compile closes the loop.

How it compares

Most Unity MCP servers are a bridge: a Python or Node server that the client talks to, plus a Unity plugin that it relays to over a socket. Those projects cover more ground than this one, with tools for ProBuilder, VFX, shaders, asset generation and more. If you need that breadth, use them.

Unity MCP takes the other trade.

	Unity MCP	Bridge-based servers
Install	One Unity package	Unity package, plus a Python or Node runtime and its server
Processes	Just Unity	Unity, the server, and the connection between them
Transport	Streamable HTTP, straight into the editor	stdio or HTTP to the server, then a socket to Unity
Updating	Package Manager	The package and the server, kept in step

What you also get here:

• Every write is one Undo step.
• Screenshots go back to the model as images.
• compile and run_tests wait for the result and return it in the same call.
• One toggle makes the whole server read-only.
• It runs in -batchmode, with no editor window.

Settings

Window → Unity MCP

This is the beginning of the README. Read the rest at the original. Read the full README ↗