Base64MCP

This is a Model Context Protocol (MCP) server that provides tools to convert base64-encoded images and image URLs into markdown-formatted image embeds for display in LLM chat interfaces (e.g., OpenWebUI chat).

Tools

• base64-to-url: Accepts base64-encoded image data (optionally prefixed with data URI), saves it as an image file, and returns a markdown snippet with a URL to display the image.
• display-url: Accepts an image URL and returns a markdown snippet to display the image.

Usage

1. Install dependencies:

   npm install

2. Start the MCP server:

   npm start

3. MCP endpoint:

   • POST requests: http://localhost:4000/mcp
   • Static images served at: http://localhost:4000/images/

Tool Integration

Clients (e.g., OpenWebUI chat) should always use the base64-to-url tool when they have base64-encoded image data, and the display-url tool when they have a direct image URL. The server will return a markdown snippet for the client to render as an image.

Example Cursor JSON

Here is an example of how an LLM client (e.g., Cursor) can invoke the base64-to-url tool to upload base64 image data:

{
  "jsonrpc": "2.0",
  "id": 1,
  "method": "base64-to-url",
  "params": {
    "data": "data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAA..."
  }
}

To display an existing image URL using the display-url tool:

{
  "jsonrpc": "2.0",
  "id": 2,
  "method": "display-url",
  "params": {
    "url": "https://example.com/path/to/image.jpg"
  }
}

Example mcpservers.json

Clients that support loading servers from a mcpservers.json file (e.g., Cursor) can register this server with an entry like:

{
  "mcpServers": {
    "base64-mcp": {
      "command": "npx",
      "args": ["-y", "@cloudwerxlab/base64-mcp"],
      "env": {
        "BASE_URL": "http://localhost:4000"
      }
    }
  }
}

Adjust the server name, package name, and BASE_URL as needed based on your environment.