Summer Engine MCP guide
How to make games in Goose with Summer Engine
Add Summer Engine as a Goose extension and let a free local model build real games through MCP — scenes, scripts, Play mode, and diagnostics. Summer Engine is the desktop game engine; Goose drives it through MCP with a model running on your own hardware.
Summer is free for MCP use
Download the desktop engine and connect it to your agent. The model runs on your own hardware, with no AI subscription and no per-message cost.
Open Goose
Run a free local model on your own GPU. The setup writes the MCP config so {agentLabel} can drive the engine directly.
Run a Summer game
The local model writes code. Summer Engine shows the Summer game, runs Play mode, and helps inspect errors. Export still requires the target templates and toolchains.
Install
Connect Summer to Goose
- 1
Install Summer Engine
Downloads the desktop engine app, about 1 GB. Skip it if Summer Engine is already installed, or if you only need assets and video for a game built in another engine.
- 2
Sign in
Opens your browser once. The CLI and the engine share the session.
- 3
Connect Goose
Writes the summer-engine MCP config and installs the Summer game-dev skills.
- 4
Restart and build
Restart Goose (CLI or Desktop); summer-engine is listed under Extensions.
Local setup notes
The 2026 specifics.
Summer is a Goose extension
The setup command adds summer-engine as a command-line extension in ~/.config/goose/config.yaml (%APPDATA%\Block\goose\config\config.yaml on Windows). Restart Goose and it is listed under Extensions. To add it by hand instead, run `goose configure` → Add Extension → Command-line Extension with the command `npx -y summer-engine@latest mcp`.
Point Goose at a local model
`goose configure` → Configure Providers → Ollama with host localhost:11434. Pick a model with native tool calling, like gpt-oss-20b or Qwen3-Coder-30B; Goose’s toolshim mode for non-tool-calling models is slower and less reliable.
Mind the context window
Ollama defaults to a 4k context on GPUs under 24 GB of VRAM — too small for MCP tool schemas. Start it with OLLAMA_CONTEXT_LENGTH=65536, and keep only a couple of extensions enabled so tool schemas leave room for actual work.
Why this matters
Goose runs free on your hardware. Summer Engine shows the game.
A capable local model can operate a real engine through MCP. It opens scenes, places objects, runs the project and reads errors. Your GPU does the thinking, with no subscription and no per-token bill, and your prompts never leave your machine.