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Use coding agents with Unity Editor.

Chat with an agent inside Unity, or expose Unity tools to DotCraft, Claude Code, Codex, Cursor, and other agents.

What you can do

Workflow	Use this when	Entry point
In-Unity Agent Chat	You want to chat with DotCraft or another ACP agent inside Unity	Tools → DotCraft → AI Assistant
MCP Tool Gateway	You want external MCP clients such as Claude Code, Codex, or Cursor to call Unity tools	Tools → DotCraft → MCP Gateway Setup
C# Automation	You want an agent to perform batch operations in Unity	unity_execute_csharp
Custom Tools	You want to expose project-specific Unity tools	[AgentTool]

In-editor ACP chat and MCP Tool Gateway are separate paths.

• In-editor chat starts an ACP agent process and talks to it inside Unity.
• MCP Tool Gateway starts a local Unity tool endpoint for external agents.

Quick Start

Install

Open Window → Package Manager and add this Git URL:

https://github.com/DotHarness/dotcraft-unity.git

Minimum Unity version: 2021.3, recommended version: Unity 6.

Option A: Chat inside Unity

1. Install dotcraft-unity from Package Manager.
2. Open Tools → DotCraft → AI Assistant.
3. Select DotCraft or Custom ACP Agent in Project Settings → DotCraft.
4. Click Connect.

Option B: Use MCP to operate Unity

1. Open the Unity project.
2. Enable Local Tool Gateway in Project Settings → DotCraft.
3. Run Tools → DotCraft → MCP Gateway Setup.
4. Choose your client: DotCraft, Claude Code, Codex, or Cursor.
5. Start your coding agent from the project root.

Option C: Add project-specific tools

1. Create a static Editor method marked with [AgentTool].
2. Let Unity compile.
3. Enable the tool in Project Settings → DotCraft → Unity Tools.
4. Use it from DotCraft or any MCP client connected to the gateway.

MCP Tool Gateway

dotcraft-unity exposes a local MCP Tool Gateway for external coding agents. While Unity Editor is running, MCP clients can connect to:

http://127.0.0.1:39777/dotcraft/mcp

Currently supports DotCraft, Claude Code, Codex, and Cursor.

The MCP endpoint uses sessionful Streamable HTTP for protocol version 2025-11-25. initialize returns MCP-Session-Id; later POST and DELETE requests must send that header. Stale or expired sessions return HTTP 404, which tells compliant clients to reinitialize. GET /dotcraft/mcp returns HTTP 405 because the gateway does not expose an SSE stream.

Built-in tools

dotcraft-unity provides one built-in Unity runtime tool based on Roslyn:

Tool	Description
unity_execute_csharp	Compile and execute a C# method-body snippet in the Unity Editor process.

Use unity_execute_csharp to read or modify scene state, selected objects, Console output, project metadata, and assets with C# snippets.

Custom tools

Unity Editor code can expose custom project tools by marking static methods with AgentToolAttribute. New custom tools are discovered in Edit → Project Settings → DotCraft → Unity Tools, default to disabled, and can be used from DotCraft or MCP clients after they are enabled.

using System.ComponentModel;
using DotCraft.Editor.Protocol;
using DotCraft.Editor.RuntimeTools;

public static class ExampleDotCraftTools
{
    [Description("Return a greeting from an example Unity plugin.")]
    [AgentTool(Namespace = "example", Name = "example_greet", Kind = AcpToolKind.Read)]
    public static object Greet([Description("Name to greet.")] string name = "Unity")
    {
        return new { message = $"Hello, {name}." };
    }
}

Method parameters are converted to a JSON Schema with Newtonsoft.Json naming rules. See Documentation~/dynamic-tools.md for the full registration contract.

DotCraft-specific features

dotcraft-unity supports additional DotCraft features to improve development efficiency while reducing agent context overhead.

ACP Extension

When using DotCraft as the ACP server, you do not need an MCP service. Built-in tools and custom tools are passed to the session through ACP extensions, reducing context overhead for non-Unity sessions.

Contributing

Contributions are welcome in DotHarness/dotcraft-unity. For the agent harness itself, use DotHarness/dotcraft.

Reference

DotCraft

Agent Client Protocol

License

Apache License 2.0