Build Games in Claude Code with Summer Engine MCP

Summer Engine in Claude Code

Claude Code (Claude for developers) supports MCP servers. With Summer Engine’s integration, Claude can modify your game scenes, add nodes, import assets, run the game, and debug, all from the same conversation where you’re writing code. This guide covers the configuration steps. The setup takes about a minute.

Prerequisites

Claude Code: The desktop app or IDE integration
Node.js: For running the MCP server (Node 18+)
Summer Engine: Installed and running with your project open

Configuration

Option 1: One-command setup (recommended)

npx -y summer-engine@latest setup claude-code --yes

This writes the summer-engine server into ~/.claude.json (Claude Code’s user-level MCP config), installs the skill library to ~/.claude/skills/, and runs summer doctor. Add --scope project to write .mcp.json in the project root and .claude/skills/ instead, so the setup travels with the game.

Option 2: Manual configuration

Step 1: Locate the Config File

Claude Code reads MCP servers from two places:

User-level: ~/.claude.json (all projects). On Windows: %USERPROFILE%\.claude.json.
Project-level: .mcp.json in the project root (shared with the team through version control; Claude Code asks once before loading it).

Create the file if it doesn’t exist. If you already have other MCP servers configured, add Summer Engine to the existing mcpServers object. Claude Code lists "type": "stdio" as required for command-based servers.

Step 2: Add Summer Engine

{
  "mcpServers": {
    "summer-engine": {
      "type": "stdio",
      "command": "npx",
      "args": ["-y", "summer-engine@latest", "mcp"]
    }
  }
}

{
  "mcpServers": {
    "other-server": { ... },
    "summer-engine": {
      "type": "stdio",
      "command": "npx",
      "args": ["-y", "summer-engine@latest", "mcp"]
    }
  }
}

You can also let Claude Code write it: claude mcp add summer-engine -- npx -y summer-engine@latest mcp.

Step 3: Restart Claude Code

Start a new Claude Code session, or run /mcp to reload servers. The server starts when Claude Code starts; it connects to the engine on the first tool call.

Step 4: Verify

When you start a conversation, Claude should have access to Summer Engine’s tools. You can ask:

“Use Summer Engine to add a Camera3D to the scene”
“Get the scene tree from Summer Engine”

If Claude says it doesn’t have access to Summer Engine tools, run /mcp to see the server list, then check the config file path and that the JSON is valid. summer doctor checks the same things from the terminal.

Using Summer Engine with Claude

Claude will use the MCP tools when your requests involve game development. You can be explicit (“Use Summer Engine to…”) or implicit (“Add a player character to the scene”). If you’re in a game project, Claude may infer that Summer Engine is the right tool. Example prompts:

“Add a CharacterBody3D named Player with a CollisionShape3D to the scene”
“Import https://example.com/barrel.glb and add it under ./World/Props”
“Set up jump and move_forward input actions for WASD and Space”
“Run the game and tell me if there are any errors in the console”
“Save the current scene to res://levels/level1.tscn”

Engine must be running. Claude’s tools talk to Summer Engine over localhost. Open your project in the engine first, or run npx summer-engine run from the project directory.

Troubleshooting

”Summer Engine is not running”

The MCP server couldn’t connect to the engine. Start Summer Engine, open your project, and try again. The engine runs a local API on port 6550; the MCP server discovers it via ~/.summer/api-token.

Config not loading

Path: Ensure the file is ~/.claude.json (user) or .mcp.json in the project root (project). ~/.claude/claude_code_config.json from older guides is not read.
JSON: Validate the syntax. No trailing commas, all strings in double quotes
Restart: Fully quit Claude Code and reopen

Claude doesn’t use the tools

Claude may not always choose MCP tools automatically. If you want to force their use, phrase your request explicitly: “Use the summer_add_node tool to add a DirectionalLight3D to the scene.”

Next Steps

Tools Reference

Every MCP tool 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.

​Summer Engine in Claude Code

​Prerequisites

​Configuration

​Option 1: One-command setup (recommended)

​Option 2: Manual configuration

​Step 1: Locate the Config File

​Step 2: Add Summer Engine

​Step 3: Restart Claude Code

​Step 4: Verify

​Using Summer Engine with Claude

​Troubleshooting

​”Summer Engine is not running”

​Config not loading

​Claude doesn’t use the tools

​Next Steps

Tools Reference

Building a Game

MCP Setup Overview

CLI Reference

Summer Engine in Claude Code

Prerequisites

Configuration

Option 1: One-command setup (recommended)

Option 2: Manual configuration

Step 1: Locate the Config File

Step 2: Add Summer Engine

Step 3: Restart Claude Code

Step 4: Verify

Using Summer Engine with Claude

Troubleshooting

”Summer Engine is not running”

Config not loading

Claude doesn’t use the tools

Next Steps