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Summer Engine: MCP server, CLI and skills

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The game engine built for AI.

Any agent builds, tests and publishes a full multiplayer game. MCP server · game-dev skills · summer CLI, in one npm package: summer-engine.

Website · Docs · CLI setup · MCP setup

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Install

• Start a game now (Node 20+): npx -y summer-engine@latest dev. It asks before it installs the Summer Engine app (about 660 MB, free) when it is missing, creates a starter project here (in ./my-game when this folder has other files) and opens it, ready for your agent. No sign-in needed to build.
• Chat apps (Claude, ChatGPT, Cursor...): add https://mcp.summerengine.com/mcp. Nothing to install.
• Homebrew: brew install summerengine/tap/summer
• npm (Node 20+): npm install -g summer-engine

CLI only (summer-engine 4.2.0 or newer), no MCP server: summer setup --cli. summer ops search "publish my game" finds any operation, signed in or not.

Connect

Cloud work: https://mcp.summerengine.com/mcp. Nothing to install. Add the URL to your agent and sign in to your Summer account once. Your agent then makes assets (images, 3D models, motion, sound effects, music, voices, video), searches and downloads your Summer asset library, plans games, and runs your projects, the store, publishing, prices, analytics, A/B tests, your team and Studio. It has no engine tools: for those, use the local server below.

Agent	Add the hosted server
Claude Code	claude mcp add --transport http summer-cloud https://mcp.summerengine.com/mcp, then /mcp to sign in
Codex	codex mcp add summer-cloud --url https://mcp.summerengine.com/mcp, then codex mcp login summer-cloud
Cursor	Add to Cursor, or add "summer-cloud": {"url": "https://mcp.summerengine.com/mcp"} under mcpServers in ~/.cursor/mcp.json
VS Code	Add to VS Code, or code --add-mcp '{"name":"summer-cloud","type":"http","url":"https://mcp.summerengine.com/mcp"}'
Devin Desktop (formerly Windsurf)	add "summer-cloud": {"serverUrl": "https://mcp.summerengine.com/mcp"} under mcpServers in ~/.config/devin/mcp_config.json (Windows %APPDATA%\devin\mcp_config.json)
Claude Desktop, claude.ai	Settings > Connectors > Add custom connector, then paste the URL

Engine work: npx -y summer-engine@latest setup <agent> --yes (needs Node 20+). It writes the local server (summer mcp) into your agent's config with the skills. The local server drives the Summer Engine app on your machine: build scenes, write scripts, play the game, take screenshots, read errors. After summer login it also runs every cloud operation, so your agent needs one server. Or paste the prompt in Get started and your agent does every step.

CLI only (summer-engine 4.2.0 or newer): npx -y summer-engine@latest setup <agent> --cli --yes. No MCP server: your agent runs Summer as commands in its shell. Setup installs the skills for your agent, with summer-cli, the guide to the commands, and writes no MCP entry. Your agent signs you in with summer login, finds an operation with summer ops search "<what you want>" and runs it as summer <area> <action> --<field> <value>, with --dry-run, --wait and --json. Engine commands (summer engine …) drive the Summer Engine app on your machine. Each skill ends with a table of the command for every tool it names. Add --assets-only for only the asset skills. --no-mcp is the same as --cli.

ChatGPT and Claude's connector directory use two reviewed store versions with a fixed tool list: https://mcp.summerengine.com/chatgpt (games, assets and generation; no publishing, no billing links) and https://mcp.summerengine.com/directory (the store, publishing and Grow reads; no image, 3D, audio or video generation). They keep their 3.x tool names and have no summer_search or summer_call. For everything else, use /mcp.

What this is

Summer Engine is the game engine built for AI. This repo connects your AI coding agent (Claude Code, Cursor, Codex, Copilot and many more) to it: the agent builds a whole game in the engine, tests it, publishes it to summer.games and reads how players play it.

Part	What it does
MCP server (summer mcp)	Tools your agent calls to drive the running editor: build scenes, write scripts, play the game, take screenshots, read errors. After summer login it also runs the cloud operations: assets, plans, the store, publishing, prices and analytics.
Skills	Game-dev know-how your agent loads: movement, combat, multiplayer, VFX, audio, UI, level design and more.
CLI (summer)	Installs the engine, signs you in, sets up your agent, creates projects from templates and publishes games.

This repo is not the engine itself. The CLI downloads the Summer Engine app for you.

With Summer installed, your agent can:…