Diagram MCP Server

A Model Context Protocol (MCP) server that renders Mermaid diagrams and Plotly charts, converting them to various image formats.

Features

• Mermaid Diagram Rendering: Convert Mermaid code to SVG, PNG, or PDF

• Plotly Chart Rendering: Convert Plotly charts to SVG, PNG, or PDF

• Image Conversion: Convert diagrams and charts to PNG, JPG, or PDF with customizable quality

• Multiple Themes: Support for default, dark, and forest themes (Mermaid)

• Customizable Output: Control dimensions, background colors, and quality settings

• TypeScript: Fully typed with Zod validation

Related MCP server: Excalidraw MCP App Server

Installation

Local Installation

pnpm install

Docker Installation

# Build and run with Docker
docker build -t diagram-mcp .
docker run -p 3000:3000 diagram-mcp

Development

# Start development server
pnpm run dev

# Build the project
pnpm run build

# Run tests
pnpm test

# Run tests with coverage
pnpm run test:coverage

# Docker commands
pnpm run docker:build    # Build Docker image
pnpm run docker:run      # Run Docker container

Usage

Available Tools

1. render_mermaid

Renders a Mermaid diagram to SVG, PNG, or PDF format.

Parameters:

• mermaidCode (string, required): The Mermaid diagram code

• format (string, optional): Output format - 'svg', 'png', or 'pdf' (default: 'svg')

• theme (string, optional): Theme - 'default', 'dark', or 'forest' (default: 'default')

• backgroundColor (string, optional): Background color (default: '#ffffff')

• width (number, optional): Custom width in pixels

• height (number, optional): Custom height in pixels

Example:

{
  "mermaidCode": "graph TD\n  A[Start] --> B[End]",
  "format": "svg",
  "theme": "default"
}

2. render_plotly

Renders a Plotly chart to SVG, PNG, or PDF format.

Parameters:

• plotlyCode (string, required): The Plotly chart code (JavaScript)

• format (string, optional): Output format - 'svg', 'png', or 'pdf' (default: 'svg')

• backgroundColor (string, optional): Background color (default: '#ffffff')

• width (number, optional): Custom width in pixels

• height (number, optional): Custom height in pixels

• responsive (boolean, optional): Make chart responsive (default: true)

• displayModeBar (boolean, optional): Show mode bar (default: false)

• displaylogo (boolean, optional): Show Plotly logo (default: false)

Example:

{
  "plotlyCode": "Plotly.newPlot('plotly-chart', [{ x: [1,2,3], y: [1,2,4], type: 'scatter' }], { margin: { t: 0 } });",
  "format": "png",
  "width": 800,
  "height": 600
}

3. convert_to_image

Converts a Mermaid diagram to PNG, JPG, or PDF image format.

Parameters:

• mermaidCode (string, required): The Mermaid diagram code

• format (string, optional): Output format - 'png', 'jpg', or 'pdf' (default: 'png')

• theme (string, optional): Theme - 'default', 'dark', or 'forest' (default: 'default')

• backgroundColor (string, optional): Background color (default: '#ffffff')

• width (number, optional): Custom width in pixels

• height (number, optional): Custom height in pixels

• quality (number, optional): Image quality 1-100 (default: 90)

Example:

{
  "mermaidCode": "graph LR\n  A[Input] --> B[Process] --> C[Output]",
  "format": "png",
  "theme": "dark",
  "quality": 95
}

MCP Configuration

Add this to your MCP client configuration:

{
  "mcpServers": {
    "diagram-mcp": {
      "command": "node",
      "args": ["dist/index.js"],
      "env": {}
    }
  }
}

sse: PORT=3919 TRANSPORT_TYPE=http npx diagram-mcp

{
  "mcpServers": {
      "diagram": {
        "command": "npx",
          "args": [   
              "-y",
              "mcp-remote",
              "http://localhost:3919/mcp",
              "--allow-http"
          ]
      }
  }
}

Supported Chart Types

Mermaid Diagrams

The server supports all Mermaid diagram types:

• Flowcharts

• Sequence diagrams

• Class diagrams

• State diagrams

• Entity Relationship diagrams

• User Journey diagrams

• Gantt charts

• Pie charts

• Git graphs

• C4 diagrams

• Mindmaps

Plotly Charts

The server supports all Plotly chart types:

• Scatter plots

• Line charts

• Bar charts

• Histograms

• Box plots

• Violin plots

• Heatmaps

• 3D plots

• Contour plots

• Surface plots

• And many more...

Examples

Mermaid Flowchart

graph TD
  A[Start] --> B{Is it working?}
  B -->|Yes| C[Great!]
  B -->|No| D[Debug]
  D --> B

Mermaid Sequence Diagram

sequenceDiagram
  participant Alice
  participant Bob
  Alice->>John: Hello John, how are you?
  loop Healthcheck
    John->>John: Fight against hypochondria
  end
  Note right of John: Rational thoughts <br/>prevail!
  John-->>Alice: Great!
  John->>Bob: How about you?
  Bob-->>John: Jolly good!

Plotly Scatter Plot

Plotly.newPlot(
  "plotly-chart",
  [
    {
      x: [1, 2, 3, 4, 5],
      y: [1, 2, 4, 8, 16],
      type: "scatter",
      mode: "lines+markers",
    },
  ],
  {
    title: "Exponential Growth",
    xaxis: { title: "X" },
    yaxis: { title: "Y" },
  }
);

Error Handling

The server provides detailed error messages for:

• Invalid Mermaid syntax

• Unsupported formats

• Browser initialization failures

• Screenshot generation errors

Dependencies

• @modelcontextprotocol/sdk: MCP SDK

• mermaid: Mermaid diagram rendering

• puppeteer: Browser automation for image conversion

• zod: Schema validation

• dotenv: Environment variable management

License

MIT