summer

# Summer: MCP server, CLI and skills for Summer Engine

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<img src="docs/brand/sun.png" alt="" width="128">

### 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`.**

[![npm](https://img.shields.io/npm/v/summer-engine?label=npm&color=f7b731)](https://www.npmjs.com/package/summer-engine)
[![downloads](https://img.shields.io/npm/dm/summer-engine?label=downloads&color=f7b731)](https://www.npmjs.com/package/summer-engine)
[![license](https://img.shields.io/badge/license-MIT-1a1a1a)](LICENSE)

[**Website**](https://www.summerengine.com) · [**Docs**](https://docs.summerengine.com) · [**CLI setup**](https://www.summerengine.com/cli) · [**MCP setup**](https://www.summerengine.com/mcp)

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## 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](https://cursor.com/install-mcp?name=summer-cloud&config=eyJ1cmwiOiJodHRwczovL21jcC5zdW1tZXJlbmdpbmUuY29tL21jcCJ9), or add `"summer-cloud": {"url": "https://mcp.summerengine.com/mcp"}` under `mcpServers` in `~/.cursor/mcp.json` |
| VS Code | [Add to VS Code](https://vscode.dev/redirect/mcp/install?name=summer-cloud&config=%7B%22type%22%3A%22http%22%2C%22url%22%3A%22https%3A%2F%2Fmcp.summerengine.com%2Fmcp%22%7D), 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 `~/.codeium/windsurf/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](#get-started-one-prompt) and your agent does every step.

**CLI only: `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](https://www.summerengine.com) 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](https://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:

- **Build real games**: scenes, scripts, physics and UI, through live MCP tools.
- **Build multiplayer games** on Summer's own networking: matchmaking, parties, leaderboards, player data and world saves.
- **Add analytics** to the game and read it back: store page views, launches, play sessions, play time and your own events.
- **Publish games** to the [summer.games](https://summer.games) store: the store page, art, the build, a private preview link and the release. Summer's store review runs before anything goes live.
- **Use proven recipes**: skills, templates and references, all searchable through one index.
- **Check its own work**: play the game, take screenshots, read the debugger, press real keys.
- **Resume any project**: `.summer/` project memory lets a fresh agent pick up where the last one stopped.

### You decide what your agent may do

Studio > Settings > Agent permissions has six switches. They apply to every app you connect, like Claude or ChatGPT. These defaults apply now. You can change them soon. Until then, Summer Games still asks the game's owner before an agent publishes, and price, A/B test and member changes ask you first.

| Switch | Default | What the agent may do without asking |
|---|---|---|
| Make and build | on | Edit drafts, scenes, plans and uploads, and start builds. |
| Spend credits | on | Generate assets and run paid builds, within your credits and your auto top-up limit. |
| Publish | on | Publish store pages, versions and releases. Summer's store review still runs first. |
| Prices and live changes | on | Change prices and sales, start or stop A/B tests, change member roles. |
| Delete for good | off: asks | Delete games, assets, pages and releases. |
| Contact people | off: asks | Send invites and other emails to real people. |

When a switch is off, the agent asks you first. It gives you a link (`https://www.summerengine.com/studio/approvals/<id>`), and an open Studio tab shows the request with Approve and Decline. Nothing changes until you approve. The agent always asks before it changes agent permissions or auto top-up, enters a jam, or changes the analytics event limit. Studio > Settings > Agent activity lists what agents changed or asked for, newest first, with Undo for prices, sales, country prices, member roles, team names and the event limit.

Generation and paid builds spend your Summer credits. Turn on auto top-up in Studio Billing: when your credits fall below an amount you pick, Summer adds the amount you choose, up to a monthly limit you set. Agents can never change auto top-up on their own. When credits run out, your agent gets the error `no_credits` with one link: https://www.summerengine.com/studio/credits.

Summer never installs software without your explicit confirmation. Library entries are structurally prevented (by a capability lint in CI) from instructing agents to touch the network, credentials, or package managers.

## Get started: one prompt

Open your AI agent (Claude Code, Cursor, Codex, Copilot, Devin Desktop, etc.) and paste:

> Install Summer Engine and let's make a game. Read github.com/summerengine/summer, check what I already have installed, install whatever is missing, log me in, and scaffold a starter project so we can start building.

The agent reads this README, checks what is already on your machine, and runs only the missing steps in its shell.

The first run will:
1. Fetch the `summer-engine` npm package (~2 MB) through npx.
2. Install Summer's game-dev skills into `~/.claude/skills/` (or your agent's user-skill directory) so the agent loads them next session.
3. Download the Summer Engine app (~1 GB, including Git and other runtime tools) if it's not installed.
4. Open your browser for one-click sign-in.
5. Scaffold a starter project and open the engine.

In most agents (Claude Code, Codex, Cursor, GitHub Copilot (VS Code, CLI, JetBrains), Zed, Cline, Kilo Code, OpenCode, Devin Desktop, Antigravity, Kiro, Trae, Warp, Goose, Hermes, Crush, Amp, Factory, Junie, Qwen Code, Kimi Code, Grok Build and Mistral Vibe), setup also connects Summer Games (`summer-games`), so the agent can see your friends, start parties and send messages as you. You sign in once; setup prints the step for your agent (Claude Code: `/mcp`, choose `summer-games`; Codex: `/mcp login summer-games`; Cursor: Connect next to `summer-games` in its MCP settings). A summer.games page opens in your browser; sign in and choose Allow.

Then ask the agent to build something.

### Claude Code: the Summer plugin

In Claude Code, type:

```text
/plugin install summer --marketplace summerengine/summer
```

Then type `/summer:start`. It signs you in and gets a first game playing in about five minutes: from a template that already plays, or from a plan of concept art Summer draws for your idea right in the chat, built in the Summer Engine desktop app. The plugin brings Summer's skills and two MCP servers: `sum