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Summer Engine in Antigravity

Antigravity is Google’s AI-powered IDE that supports MCP (Model Context Protocol). With Summer Engine’s integration, Antigravity’s AI can control your game engine: add nodes to scenes, set properties, import assets, run the game, and debug, all from within your coding workflow. This guide covers the configuration. Setup takes about a minute.

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Prerequisites

  • Antigravity: Google’s AI-powered IDE
  • Node.js: For running the MCP server (Node 18+)
  • Summer Engine: Installed and running with your project open

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Configuration

Antigravity uses the VS Code MCP config format. The config file is:
  • Project-level: .vscode/mcp.json in your project root
  • Global: Use the Antigravity CLI (antigravity --add-mcp) if available
Config format. Antigravity uses servers (not mcpServers). The structure matches VS Code’s MCP configuration.

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Step 1: Create or Edit the Config File

Create .vscode/mcp.json in your project root. If the file already exists (e.g., for other MCP servers), add Summer Engine to the existing servers object.

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Step 2: Add Summer Engine

{
  "servers": {
    "summer-engine": {
      "command": "npx",
      "args": ["summer-engine", "mcp"]
    }
  }
}

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Step 3: Restart Antigravity

Close and reopen Antigravity so it loads the new MCP config. The Summer Engine MCP server starts when Antigravity starts; it connects to the engine on the first tool call.

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Step 4: Verify

Check Antigravity’s MCP or AI settings to confirm “summer-engine” appears with 23 tools. Then try a prompt:
  • “Use Summer Engine to add a MeshInstance3D with a BoxMesh to the scene”
If the node appears in Summer Engine, the setup is working.

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Using Summer Engine with Antigravity

Once configured, the AI can use Summer Engine’s tools when you ask for game-related changes. Example prompts:
  • “Add a Camera3D and DirectionalLight3D to the scene root”
  • “Get the scene tree from Summer Engine”
  • “Import this model and add it to the World node: [URL]”
  • “Run the game and capture a screenshot”
  • “Set the project’s main scene to res://main.tscn”
Engine must be running. Antigravity’s AI talks to Summer Engine over localhost. Open your project in the engine first, or run npx summer-engine run from the project directory.

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Troubleshooting

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”Summer Engine is not running”

Start Summer Engine and open your project. The MCP server connects to the engine’s local API on port 6550. The engine writes a token to ~/.summer/api-token when it starts.

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MCP server not appearing

  • Config path: Verify .vscode/mcp.json is in your project root (the folder you opened in Antigravity)
  • JSON validity: Ensure no trailing commas, proper quotes, and valid JSON structure
  • Restart: Fully quit and reopen Antigravity

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Tools return errors

See the Tools Reference for parameter formats. Common issues: wrong node path format (./World/Player), invalid property values (use engine string format like "Vector3(0, 10, 0)"), or the game running when scene edits are attempted (stop it first with summer_stop).

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Next Steps

Tools Reference

All 23 MCP tools with parameters and examples

Building a Game

How an AI builds a full game using MCP

MCP Setup Overview

Architecture, prerequisites, and other IDEs

CLI Reference

summer install, run, create, and more
Need help or have questions? Reach out to our founders at founders@summerengine.com or join our community on Discord for fast responses.