Unity MCP: Free and Open-source. Ideal if you want to extend the MCP functionality for your own use cases

Coplay: Premium AI Assistant for Unity, which is much more capable than the Unity MCP. See this post for a comparison. Coplay is the easiest way to quickly get started with the best AI assistant for Unity.

Coplay MCP: An MCP interface for Coplay. It's slightly harder to set up than Coplay, but it allows you to use your existing AI subscription (e.g., Claude Code or ChatGPT) to leverage most of Coplay's features for free. Coplay MCP is much more capable than Unity MCP, but it's not open-source and extensible. Coplay MCP does not have access to some of the Coplay features such as; automating pipelines, limited visual feedback, Unity project specific initial context.