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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 OpenCode

OpenCode is an open-source terminal agent that supports MCP (Model Context Protocol). With Summer Engine’s integration, OpenCode 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.

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Prerequisites

  • OpenCode: The open-source 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 OpenCode config, installs the recommended skills, and runs diagnostics: 
npx -y summer-engine@latest setup opencode --yes
This writes to your user OpenCode config (~/.config/opencode/opencode.json on macOS and Linux, %APPDATA%\opencode\opencode.json on Windows). For a single project, use --scope project to write opencode.json in the project root instead.

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Option 2: Manual configuration

Create or edit your OpenCode config and add the summer-engine MCP server. OpenCode uses a command array and an environment object: 
{
  "$schema": "https://opencode.ai/config.json",
  "mcp": {
    "summer-engine": {
      "type": "local",
      "command": ["npx", "-y", "summer-engine@latest", "mcp"]
    }
  }
}
To preview the exact config without writing files, run: 
npx -y summer-engine@latest setup opencode --print

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Restart OpenCode

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

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Verify

List your MCP servers in OpenCode 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 OpenCode

Once configured, OpenCode 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. OpenCode 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 the config exists at ~/.config/opencode/opencode.json (or opencode.json in the project root for project scope)
  • JSON validity: Ensure no trailing commas and valid JSON
  • Restart: Fully quit and reopen OpenCode
  • 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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