Summer Engine CLI

CLI and MCP tools for Summer Engine — the AI-native game engine. MIT licensed.

Install

npm install -g summer-engine

Or use without installing:

npx summer-engine <command>

Quickstart (under 2 minutes)

summer install                       # Download the engine
summer login                         # Sign in via browser
summer create 3d-basic my-game       # Create a starter project
summer run my-game                   # Open it in the engine
summer setup claude-code --yes       # Configure MCP + install recommended skills

Replace claude-code with codex, cursor, or windsurf. Add --scope project to keep the configuration inside the project.

Verify:

summer doctor

Then open your agent and try one of the slash commands:

| Command | What it does | |---|---| | /debug | Triage and fix a bug end-to-end (reads engine errors, locates code, proposes fix) | | /play | Run the game and report state (clean run, warnings, or crash) |

Or just describe what you want — the specialist skills (FPS controller, lighting, GDScript patterns, scene composition, UI, asset strategy) auto-trigger on natural language: "make me an FPS", "add lighting", "I need a HUD".

Commands

| Command | Description | |---------|-------------| | summer install | Download and install Summer Engine | | summer login | Sign in via browser (Google/GitHub) | | summer logout | Clear auth tokens | | summer status | Check engine status, port, auth state | | summer doctor | Diagnose Node, login, engine, local API, MCP boot | | summer run [path] | Launch engine (optionally with a project) | | summer open <path> | Open a project in the running engine | | summer create <template> [name] | Create new project from template | | summer list templates \| projects | List available templates or local projects | | summer skills list | Show available skills | | summer skills install <name> | Install one skill | | summer skills install --recommended --agent <agent> | Install the recommended set | | summer mcp | Start the MCP server (used by Codex/Cursor/Claude Code/Windsurf) | | summer mcp setup <agent> | Write MCP config for an agent | | summer setup <agent> | One shot: MCP config + recommended skills + doctor |

Supported agents: codex, claude-code, cursor, windsurf. Supported scopes: user (default), project.

Plugin install (Claude Code)

claude /plugin install summer-engine

That registers Summer as a plugin under the summer: namespace. Skills appear in the slash menu as summer:brainstorm-game, summer:debug, summer:play, etc. The plugin also bundles:

• A summer-engine MCP server (configured automatically — no manual ~/.claude.json edit needed).
• Lifecycle hooks: a session-start greeter that detects Godot/Summer projects and reads .summer/GameSoul.md; a pre-commit-doctor hook (opt-in) that runs summer doctor before commits.

For Cursor, Codex, OpenCode, and Gemini, see docs/CURSOR.md, docs/CODEX.md, and the manifests at .cursor-plugin/, .codex-plugin/, .opencode/, gemini-extension.json respectively.

MCP Integration

summer setup <agent> writes the right config in the right place. If you need to do it by hand:

Cursor (.cursor/mcp.json per project, or ~/.cursor/mcp.json user-wide):

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

Claude Code (~/.claude.json user-wide, or .mcp.json per project):

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

Codex (~/.codex/config.toml):

[mcp_servers.summer-engine]
command = "npx"
args = ["summer-engine", "mcp"]

The MCP server exposes focused tools for scene manipulation, inspector/resource ops, project settings, asset import, play/stop, diagnostics, and asset search/generation. Tools the host agent already has natively (file ops, git, shell, grep) are intentionally not exposed.

Visual feedback (viewport and game screenshots) is currently available in the Summer Engine app via the built-in Summer Agent. MCP support for screenshots is on the MVP2 roadmap, gated on host clients reliably consuming image content.

How It Works

1. Summer Engine runs a local API server on localhost:6550.
2. The MCP server (npx summer-engine mcp) connects to that local API via a per-machine auth token (~/.summer/api-token) and exposes engine ops as MCP tools.
3. Agents call the MCP tools and edit .gd/.cs/.json/.md files directly with their own file tools. Scenes (.tscn) flow through MCP.

The engine must be running for MCP tools that touch scenes/assets/diagnostics. If it isn't, tools return a clear error pointing at summer run.

Per-Agent Docs

• Agent Kit overview
• Claude Code
• Codex
• Cursor
• Skills overview
• Templates overview

Templates

Built-in templates:

• empty — Empty 3D project with a root node
• 3d-basic — 3D scene with camera, light, and floor

More templates coming soon.

Links

• Website
• Documentation
• Community