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Documentation Index

Fetch the complete documentation index at: https://docs.summerengine.com/llms.txt

Use this file to discover all available pages before exploring further.

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Summer Engine in GitHub Copilot CLI

GitHub Copilot CLI is GitHub’s terminal agent, and it supports MCP (Model Context Protocol). With Summer Engine’s integration, Copilot can control your game engine: add nodes to scenes, set properties, search and import assets, generate images and 3D models, run the game, and debug, all from the terminal. This guide covers the configuration. Setup takes about a minute.
This page covers GitHub Copilot CLI. For Copilot inside VS Code, see the VS Code setup.

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Prerequisites

  • GitHub Copilot CLI: GitHub’s terminal agent
  • Node.js: For running the MCP server (Node 18+)
  • Summer Engine: Installed and running with your project open

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Configuration

Run the Summer setup command. It writes the Copilot MCP config, installs the recommended skills, and runs diagnostics: 
npx -y summer-engine@latest setup github-copilot --yes
This writes the config to ~/.copilot/mcp-config.json (user scope). For a single project, use --scope project to write .mcp.json in the project root instead.

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Option 2: Manual configuration

Create or edit ~/.copilot/mcp-config.json and add the summer-engine server. If the file already exists, add summer-engine to the mcpServers object: 
{
  "mcpServers": {
    "summer-engine": {
      "type": "local",
      "command": "npx",
      "args": ["-y", "summer-engine@latest", "mcp"],
      "tools": ["*"]
    }
  }
}
To preview the exact config without writing files, run: 
npx -y summer-engine@latest setup github-copilot --print

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Restart Copilot CLI

Close and restart Copilot CLI so it loads the new config. The Summer Engine MCP server starts with Copilot; it connects to the engine on the first tool call.

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Verify

List your MCP servers in Copilot CLI and confirm summer-engine appears with its 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 Copilot CLI

Once configured, Copilot 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”
  • “Generate a low-poly treasure chest and import it under the World node”
  • “Run the game and read the diagnostics”
  • “Set the project’s main scene to res://main.tscn”
Engine must be running. Copilot 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 ~/.copilot/mcp-config.json exists (or .mcp.json in the project root for project scope)
  • JSON validity: Ensure no trailing commas and valid JSON
  • Restart: Fully quit and reopen Copilot CLI
  • Diagnostics: Run npx -y summer-engine@latest doctor to check the MCP server boot, login, and engine connection

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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 44 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 setup, doctor, run, create, and more
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