Deprecated. use https://github.com/WHedlund/csharp-sdk instead

Unity EmbedIO Extensions for the MCP C# SDK

Unstable: This package tracks the evolving Model Context Protocol (MCP) and is subject to breaking changes as the MCP package updates.

About

This package enables Unity projects to run a fully functional Model Context Protocol (MCP) server using EmbedIO as a lightweight HTTP server. It is designed specifically for Unity, since ASP.NET Core is not fully compatible with the Unity runtime (Mono).

Key features:

• Native Unity integration for MCP servers.
• Uses EmbedIO for lightweight HTTP/SSE transport.
• Runs the HTTP server in a separate thread to avoid blocking the Unity main thread.
• A MainThreadDispatcher may be added for safe Unity object interaction.
• Automatic tool discovery: Finds tools on the same GameObject (see EchoToolWithInstance).
• Updated to match latest MCP type/name changes.

This is a community-driven project and not officially maintained by the MCP core team.

🚀 Installation & Getting Started

1. Add This Package to Your Unity Project

Simply clone or copy this repository into your project’s Assets folder.

Assets/
└── ModelContextProtocol/
    └── EmbedIO/
        ... (all scripts here)

2. Install Dependencies

Use NuGet for Unity to install the required packages:

• EmbedIO 3.5.2
• ModelContextProtocol 0.1.0-preview.10

Enable "Show Prerelease Packages" in NuGet for Unity’s settings to find the correct MCP version.

3. Add Components to Your Scene

1. Create a new GameObject in your Unity scene.
2. Attach both EmbedIOServerHost and EchoToolWithInstance scripts to this GameObject.

When you press Play, the MCP server starts automatically (in a background thread) and is available at:

http://localhost:8888/api/sse

You can test your server using the MCP Inspector tool from MCP[cli].

To add more tools, just add additional tool scripts as components on the same GameObject for automatic discovery!

🧩 Usage & Examples

Tools are automatically discovered when added as components to the same GameObject as the server host.
Here’s an example of an instance tool using MonoBehaviour:

using UnityEngine;
using ModelContextProtocol.Tools;

public class EchoToolWithInstance : MonoBehaviour
{
    [McpServerTool(Description = "Echoes the input message (instance)")]
    public string Echo(string message)
    {
        return $"Echo: {message}";
    }
}

• Attach your tool script (like EchoToolWithInstance) to the same GameObject as EmbedIOServerHost.
• All [McpServerTool] methods will be registered and available to MCP clients.
• You can test tool calls using MCP Inspector or any MCP-compatible client.

🔗 Related Projects & Links

• ModelContextProtocol C# SDK (NuGet)
• ModelContextProtocol.AspNetCore (reference)
• Official Model Context Protocol Specification
• MCP Inspector (Python SDK/CLI tool)