Unity Code MCP Server

Powerful tool for the Unity Editor that gives AI Agents ability to perform any action using Unity Editor API, like modification of scripts, scenes, prefabs, assets, configuration and more.

Inspect active scenes, components, assets, console output, settings, Play Mode state, and runtime values from an MCP client.

Create and modify GameObjects, prefabs, ScriptableObjects, import settings, and other Unity assets by executing C# in the Editor.

Run Edit Mode and Play Mode tests, enter Play Mode, simulate player input, capture screenshots, read Unity console logs, and inspect live game state after actions.

Example agent workflow: Play Pong in a closed loop by usingenter_play_mode,execute_csharp_script_in_unity_editor,play_unity_game, andread_unity_console_logsto search runtime state, execute input actions, verify the result, and adapt the next move.

Seethe full cities workflow example and transcript.

- Tools
- Security considerations
- Architecture
- Quick start
- Built-in tools
- Agent skills
- Extending (adding tools)
- Script execution context
- STDIO bridge
- Testing
- Known Issues
- License

graph LR A["MCP Client<br/>AI Agent"] -->|STDIO| B["STDIO Bridge<br/>Python script"] B <-->|request/response files| C["Unity Code MCP Server<br/>Unity Editor"] style A fill:#e1f5ff style B fill:#fff3e0 style C fill:#f3e5f5

- Unity 2022.3 LTS or higher (tested on 2022.3.62f3 and 6000.2.7f2)
- uv(Python package manager) for the bundled STDIO bridge:https://docs.astral.sh/uv/.

- Follow instructions athttps://docs.astral.sh/uv/getting-started/installation

https://github.com/Signal-Loop/UnityCodeMCPServer.git?path=Assets/Plugins/UnityCodeMcpServer

{ "mcpServers": { "unity-code-mcp-stdio": { "command": "uv", "args": [ "run", "--directory", "C:/path/to/UnityProject/Assets/Plugins/UnityCodeMcpServer/Editor/STDIO~", "unity-code-mcp-stdio" ] } } }

- Access the settings viaTools/UnityCodeMcpServer/Show or Create Settings.
- ConfigureVerbose Loggingfor detailed diagnostics and optionally setInput Actions Assetforplay_unity_game.

The file-backed transport exchanges request and response files through.unityCodeMcpServer/messagesin the Unity project root.

- Tools/UnityCodeMcpServer/Show or Create Settings— Open the server settings asset in the inspector

Unity Code MCP Server ships a set ofAI agent skill files(Markdown documents that teach your agent how to use the server's tools effectively). These skills are installed automatically into the configured target directory whenever the package is installed or updated.
- Open the server settings:Tools/UnityCodeMcpServer/Show or Create Settings.
- Scroll to theSkillssection.
- Choose the install directory from the dropdown:

- GitHubtargets.github/skills/
- Claudetargets.claude/skills/
- Agentstargets.agents/skills/
- Customshows a folder picker so you can select any directory
- The inspector shows the currently selected target directory label so you can verify exactly where skills will be copied.
- Package install and update runs copy the skills automatically.

Only new or changed.mdfiles are copied. Files that are already up to date (matching content hash) are skipped.

Add Tools, Prompts, Resources, or Async Tools by implementing the relevant interfaces (ITool, IToolAsync, IPrompt, IResource) anywhere in your codebase. The server will automatically detect and register them.

using System.Collections.Generic; using Newtonsoft.Json.Linq; using UnityCodeMcpServer.Interfaces; using UnityCodeMcpServer.Protocol; public class EchoTool : ITool { public string Name => "echo"; public string Description => "Echoes the input text back to the caller"; public JToken InputSchema => JsonHelper.ParseElement(@"{ ""type"": ""object"", ""properties"": { ""text"": { ""type"": ""string"", ""description"": ""The text to echo"" } }, ""required"": [""text""] }"); public ToolsCallResult Execute(JToken arguments) { var text = arguments.GetStringOrDefault("text", ""); return ToolsCallResult.TextResult($"Echo: {text}"); } }

using System.Collections.Generic; using Newtonsoft.Json.Linq; using UnityCodeMcpServer.Interfaces; using UnityCodeMcpServer.Protocol; using System.Threading.Tasks; public class DelayedEchoTool : IToolAsync { public string Name => "delayed_echo"; public string Description => "Echoes the input text after a specified delay (demonstrates async tool)"; public JToken InputSchema => JsonHelper.ParseElement(@"{ ""type"": ""object"", ""properties"": { ""text"": { ""type"": ""string"", ""description"": ""The text to echo"" }, ""delayMs"": { ""type"": ""integer"", ""description"": ""Delay in milliseconds before echoing"", ""default"": 1000 } }, ""required"": [""text""] }"); public async Task<ToolsCallResult> ExecuteAsync(JToken arguments) { var text = arguments.GetStringOrDefault("text", ""); var delayMs = arguments.GetIntOrDefault("delayMs", 1000); await Task.Delay(delayMs); return ToolsCallResult.TextResult($"Delayed Echo (after {delayMs}ms): {text}"); } }

By default, script execution context includes following assemblies:

- Assembly-CSharp
- Assembly-CSharp-Editor
- System.Core
- UnityEngine.CoreModule
- UnityEditor.CoreModule

Unity Code MCP Server settings (Assets/Plugins/UnityCodeMcpServer/Editor/Resources/UnityCodeMcpServerSettings.asset) allow configuring additional assemblies to include in the script execution context. This is useful if your project has assemblies that your generated scripts need to reference.

To add additional assemblies use settings 'Additional Assemblies' section.

See the bridge docs atREADME_STDIO.md.

- Unity Code MCP Server includes dll files in its package. If those files are already present in your project, you may see GUID conflicts. In our test cases it does not cause any issues, but if you encounter problems, please fill issue:Issues. Removing duplicate dlls from your project may resolve the conflicts.

GUID [eb9c83041c7a89c46bb6e20eab4484df] for asset 'Packages/com.signal-loop.unitycodemcpserver/Editor/Bin/Microsoft.CodeAnalysis.CSharp.dll' conflicts with: '[Path to dll file in your project]/Microsoft.CodeAnalysis.CSharp.dll' (current owner) We can't assign a new GUID because the asset is in an immutable folder. The asset will be ignored.

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