AGMS2

GameMaker projects in VS Code, Cursor and your AI agent.

Edit GML with completions, hover docs and diagnostics, browse and change your project's objects, scripts and rooms from the editor, and give agents the same access through a local MCP server.

Install · Features · MCP server · How it works · FAQ

Features

Writing GML

• Syntax highlighting for GML, generated from a catalog of GameMaker built-in functions, variables and constants.

• Completions for built-ins, your project's assets, and functions defined in open GML files.

• Hover docs and signature help for built-in functions, plus hover details for assets (an object's sprite and parent).

• Go to definition for functions in open files and for asset names, including asset names in strings.

• Lightweight diagnostics for unmatched braces and possibly undefined identifiers.

• Schema validation for .yy and .yyp files.

Your project in the editor

• A GMS2 Project Explorer in the activity bar with Objects, Scripts, Rooms, Sprites and the other asset types. Objects expand into their events; click a script or event to open its code.

• Create objects and scripts, add events, set an object's sprite or parent, and delete assets from the explorer or the Command Palette. AGMS2 writes the .yy files and updates the .yyp for you.

• Search GML across the whole project and jump to a result.

• A room preview that plots each room's instances, and an object inspector that lists an object's events.

• Build and run commands that call the GameMaker executable you configure (Windows target only).

• A status bar item that shows the MCP server connection and reconnects with a click.

For AI agents

• A local MCP server with 27 tools to read and edit scripts and events, create and rename assets, place instances in rooms, set macros, search and replace GML, and build the project.

• Resources for project metadata, the asset tree, config, macros, extensions, and individual assets, scripts, rooms and object events.

• Prompts to audit an object, describe the project, and find usages.

• It watches the project and tells clients when assets change.

• GML skill guides in packages/gml-skills that you can point an agent at for idiomatic GameMaker code.

Related MCP server: gm-forge-mcp

Install

1. Download agms2-vsc-extension-<version>.vsix from the Releases page.

2. In VS Code or Cursor, open the Command Palette and run Extensions: Install from VSIX…, then pick the file. From a terminal, code --install-extension agms2-vsc-extension-<version>.vsix (or cursor --install-extension …) does the same.

3. Run GMS2: Open Project and choose your .yyp. The first time, choose Enable Bundled Server to use the MCP server that ships inside the extension.

4. The status bar shows GMS2: Connected and the GMS2 Project Explorer fills in.

The extension runs the server with the editor's own runtime, so editing a project needs nothing else installed. Building or running a game needs GameMaker installed and gms2.gmsBinaryPath set.

Using the MCP server with agents

The server speaks MCP over stdio. Any MCP client that can launch a local command can use it, such as Claude Code, Claude Desktop, Cursor or VS Code.

1. Get the server. Either use the copy bundled in the installed extension:

(On Windows, ~ is %USERPROFILE%.) Or build it from source, which gives you packages/mcp-server/dist/index.js:

git clone https://github.com/Sayarinu/AGMS2.git
cd AGMS2
pnpm install
pnpm -r build

2. Point your client at it. Most clients take an mcpServers entry like this (Claude Desktop's claude_desktop_config.json, Cursor's .cursor/mcp.json):

{
  "mcpServers": {
    "gms2": {
      "command": "node",
      "args": ["/absolute/path/to/server/index.js", "--project", "/absolute/path/to/MyGame.yyp"]
    }
  }
}

With Claude Code:

claude mcp add gms2 -- node /absolute/path/to/server/index.js --project /absolute/path/to/MyGame.yyp

Choosing the project. The server opens the .yyp given by --project (a .yyp file or the folder containing it), then GMS2_PROJECT_PATH, then the first .yyp in the working directory or one of its parents.

Building from an agent. Put a gms2-mcp.config.json next to the .yyp, or set the matching environment variables:

{
  "gmsBinaryPath": "C:/Program Files/GameMaker/GameMaker.exe",
  "buildTarget": "Windows",
  "watchMode": true
}

GMS2_GMS_BINARY_PATH and GMS2_BUILD_TARGET override the file.

Legacy SSE clients. Add --sse --port 3001 to also serve the older HTTP+SSE transport at http://127.0.0.1:3001/sse, on localhost only.

How it works

 VS Code / Cursor                                     MCP clients (agents)
┌────────────────────────────────────┐               ┌──────────────────────┐
│ AGMS2 extension                    │               │ Claude Code, Cursor, │
│  • GML grammar, completions, hover │               │ Claude Desktop, ...  │
│  • Project Explorer, commands      │               └──────────┬───────────┘
│  • Room preview, object inspector  │                          │ stdio
└─────────────────┬──────────────────┘                          │
                  │ stdio (MCP)                                  │
                  ▼                                              ▼
        ┌──────────────────────────────────────────────────────────────┐
        │ AGMS2 MCP server (packages/mcp-server)                       │
        │  tools · resources · prompts · file watcher                  │
        └──────────────────────────────┬───────────────────────────────┘
                                       │ reads and writes
                                       ▼
                     MyGame.yyp, objects/*/*.yy, *.gml, rooms/*/*.yy

The extension starts its own copy of the server for the open project and uses the same tools agents do, so the explorer, commands and agents all go through one implementation. The server edits GameMaker's files directly and keeps the .yyp resource list and room order in step. Editor features such as completions and hover docs come from the built-in catalog in packages/gml-skills/data/builtins.json.

FAQ

Do I need GameMaker installed? Only to build or run a game. Reading and editing a project works without it.

Does it work with any GameMaker version? It targets the GameMaker 2.3+ project format (.yyp with .yy files per asset). New assets are written in that format; recent GameMaker versions upgrade them when they load the project.

Should GameMaker be open while I edit with AGMS2? Save and close the project in GameMaker first, or reload it afterwards. Both tools write the same files.

Is my project sent anywhere? No. The server runs on your machine and only reads and writes files in your project. An AI agent you connect sees whatever its tools return, under that agent's own terms.

Does it work in VSCodium or other VS Code forks? It uses only standard extension APIs, so it should, but AGMS2 is developed against VS Code and Cursor.

Contributing

Bug reports, ideas and pull requests are welcome. Please open an issue first for larger changes. AGENTS.md has the setup, commands, architecture notes and branch and commit rules.

pnpm install
pnpm -r build
pnpm -r typecheck
pnpm test

License

AGMS2 is free and open-source software under the MIT License.

Disclaimer

AGMS2 is an independent, unofficial project. It is not affiliated with, endorsed by or sponsored by YoYo Games Ltd. or Opera Norway AS. GameMaker is a trademark of YoYo Games Ltd., part of the Opera group.