GenImgMCP 🎨

Local MCP (Model Context Protocol) server for image generation and editing using the google/gemini-3.1-flash-image model via OpenRouter.

Designed specifically for coding agents (such as Antigravity, Claude Code, Cursor, and other MCP clients), saving images directly to the project's local file system and returning the file path and structured metadata in a lightweight manner (without cluttering the context window with Base64 strings).

✨ Features

• 🖼️ Image Generation (generate_image): Create images from detailed text prompts.

• 🖌️ Image Editing and Variations (edit_image): Transform, refine, or add elements to existing images on disk.

• 💾 Automatic Local Saving: Saves image files directly to the project directory requested by the agent (or in ./generated_images/).

• ⚡ Lightweight & Efficient Response: Returns only the absolute file path and metadata (size, format, aspect ratio), preserving the caller LLM's context tokens.

• 📐 Aspect Ratio & Format Control: Supports multiple aspect ratios (1:1, 16:9, 9:16, 4:3, 3:4, 3:2, 2:3, 21:9) and file formats (png, webp, jpeg).

• 🔄 Model Flexibility: Defaults to google/gemini-3.1-flash-image, with support for any multimodal model available on OpenRouter.

Related MCP server: openrouter-imgen-mcp

🚀 Installation and Build

1. Prerequisites

• Node.js 18 or higher

• OpenRouter API Key

2. Install Dependencies and Build

# In the project root:
npm install
npm run build

⚙️ Configuration

You can configure the API key in one of three ways:

1. Environment Variable: Set OPENROUTER_API_KEY in your environment.

2. .env File: Create a .env file in the root of the project:

   OPENROUTER_API_KEY=sk-or-v1-xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
   DEFAULT_IMAGE_MODEL=google/gemini-3.1-flash-image
   DEFAULT_OUTPUT_DIR=./generated_images

3. Command Line Argument: Pass --api-key <your_key> in arguments when starting the server.

🛠️ Available Tools

1. generate_image

Generates a new image based on a text prompt.

2. edit_image

Modifies an existing image provided by local file path.

🔌 How to Integrate with MCP Clients

Configuration in Claude Desktop (claude_desktop_config.json)

{
  "mcpServers": {
    "genimg": {
      "command": "node",
      "args": [
        "D:/MyProjs.Github/GenImgMCP/dist/index.js"
      ],
      "env": {
        "OPENROUTER_API_KEY": "sk-or-v1-your-key-here"
      }
    }
  }
}

Configuration in Antigravity / Cursor / MCP Config (mcp_config.json)

{
  "mcpServers": {
    "genimg": {
      "command": "node",
      "args": [
        "D:/MyProjs.Github/GenImgMCP/dist/index.js"
      ],
      "env": {
        "OPENROUTER_API_KEY": "sk-or-v1-your-key-here"
      }
    }
  }
}

🧪 Testing the Server Locally

You can run the server directly in the terminal to verify startup:

node dist/index.js

The server will start and wait for JSON-RPC messages on the stdio channel.

📄 License

MIT