Nano Banana - OpenRouter MCP Server

Fast, cost-efficient image generation and editing for MCP. Powered by Nano Banana 2 via OpenRouter.

Features

• edit_or_create_image: Create or edit an image using the Nano Banana 2 model on OpenRouter. Fast, cost-efficient results. Supports up to 12 context images. Saves to project folder by default.

• batch_edit_or_create_images: Perform multiple image creation or editing tasks in a single batch. Optimized for Nano Banana 2. Perfect for fast, cost-efficient creative workflows.

• health_check: Validate .env loading, API key presence, selected model, and optionally run a live OpenRouter connectivity test.

• start_annotation: Open a visual annotation UI to draw on images and add notes before editing.

• get_annotation_results: Retrieve completed annotation results after the user clicks Finish.

• complete_annotation_edit: One-step helper that retrieves completed annotations and immediately applies the requested edit.

• Multimodal Support: Provide up to 12 local images as context for editing or inspiration.

• Flexible Output: Specify a local path to save each generated image.

• Model Override: Still supports NANO_BANANA_MODEL_ID if you want to point the server at a different OpenRouter image model.

Setup

Prerequisites

• Node.js and npm installed.

• An OpenRouter API key.

Installation

1. Clone this repository:

   git clone https://github.com/BearThreat/nano-banana-openrouter-mcp
   cd nano-banana-openrouter-mcp

2. Install dependencies:

   npm install

3. Build the server:

   npm run build

Configuration

Add the server to your MCP settings file (e.g., cline_mcp_settings.json or claude_desktop_config.json):

{
  "mcpServers": {
    "nano-banana": {
      "command": "node",
      "args": ["/path/to/nano-banana-openrouter-mcp/build/index.js"],
      "cwd": "/path/to/nano-banana-openrouter-mcp",
      "env": {
        "OPENROUTER_API_KEY": "your-openrouter-api-key",
        "NANO_BANANA_MODEL_ID": "google/gemini-3.1-flash-image-preview"
      },
      "disabled": false,
      "autoApprove": [
        "edit_or_create_image",
        "batch_edit_or_create_images",
        "start_annotation",
        "get_annotation_results",
        "complete_annotation_edit",
        "health_check"
      ]
    }
  }
}

Usage

Once configured, your AI client will have access to the image generation tools.

By default, this server now targets Nano Banana 2 on OpenRouter:

google/gemini-3.1-flash-image-preview

This was chosen for better speed/cost tradeoffs. You can still override it with NANO_BANANA_MODEL_ID if needed.

Single Image Generation

{
  "prompt": "Generate a modern technical infographic about the Model Context Protocol.",
  "outputPath": "infographic.png"
}

Batch Image Generation

{
  "tasks": [
    { "prompt": "Create a blue circle", "outputPath": "circle.png" },
    { "prompt": "Create a red square", "outputPath": "square.png" },
    { "prompt": "Combine circle.png and square.png into a single composition", "imagePaths": ["circle.png", "square.png"], "outputPath": "combined.png" }
  ]
}

Image Annotation

Use the start_annotation tool to open a browser-based annotation UI where you can draw freehand markings on images and add notes:

{
  "imagePaths": ["photo1.jpg", "photo2.png", "design.webp"]
}

This opens a visual editor where you can:

• Draw on each image with freehand markings (red, yellow, green, blue, white colors)

• Navigate between images with Back/Next buttons

• Add notes under each image (pre-filled with Notes about {filename}:)

• Combine all prompts into a single combined prompt when finished

The tool returns:

• annotatedImagePaths: Paths to the annotated images (saved in .nano-banana-temp/ folder)

• combinedPrompt: All individual prompts concatenated together

• originalImagePaths: The original input paths

This is particularly useful when you want to point out specific areas in images that need editing, which the AI can then use with edit_or_create_image.

Annotation Shortcut Flow

If the user has already completed the annotation step in the browser, you can call complete_annotation_edit to retrieve the saved annotation results and immediately apply the edit in one tool call.

Health Check

Use health_check to verify local configuration and optionally test OpenRouter connectivity:

{
  "testApi": true
}

License

MIT