Diagram Bridge MCP Server

A comprehensive MCP server that bridges the gap between LLMs and diagram creation through three powerful, independent tools: intelligent format selection, format-specific instruction generation, and professional diagram rendering (using kroki server). Each tool can be used standalone or combined in sequence for complete diagram workflows - from choosing the right format to generating the final image.

Supported Formats: Mermaid, PlantUML, C4 Model, D2, GraphViz, BPMN, Structurizr, Excalidraw, Vega-Lite

🚀 Quick Start

1. Prerequisites:
- Node.js 18.0 or higher
- Docker and Docker Compose

2. Install and build:

git clone git@github.com:tohachan/diagram-bridge-mcp.git

cd diagram-bridge-mcp

npm install && npm run build

3. Start services:

docker-compose up --build

4. Add to Cursor (or any MCP client):

{

  "mcpServers": {

    "diagram-bridge-mcp": {

      "command": "node",

      "args": ["/path/to/diagram-bridge-mcp/dist/index.js"],

      "enabled": true

    }

  }

}

5. Start using: The server provides three MCP tools ready for use!

💡 Usage Example

Here's a simple prompt to demonstrate the complete workflow:

"Choose the best diagram format for visualizing a current project architecture, then generate the diagram code and render it to an image file. Save the result as 'architecture-diagram'."

This single prompt will:
1. Analyze your request and recommend the optimal format
2. Get specific instructions for creating the diagram in that format
3. Create and render the final diagram to a PNG/SVG file

🎨 Examples Gallery

Want to see what's possible? Check out Examples Gallery

🛠️ Tools Overview

help_choose_diagram

Purpose: Intelligent format selection based on your requirements

- Analyzes your request using AI-powered heuristics
- Provides confidence-scored recommendations
- Works with format constraints when needed
- Generates structured prompts for optimal LLM decision-making

Example: "I need to show database relationships" → Recommends Mermaid ER diagram format with detailed reasoning

get_diagram_instructions

Purpose: Generate format-specific coding instructions

- Creates tailored prompts for any supported diagram format
- Includes syntax guidelines, best practices, and common pitfalls
- Provides working examples and output specifications
- Ensures LLMs generate syntactically correct diagram code

Example: For Mermaid format → Detailed Mermaid syntax guide with examples

render_diagram

Purpose: Transform diagram code into professional images

- Renders diagrams via integrated Kroki service
- Supports PNG and SVG output formats
- Includes intelligent caching for performance
- Provides file storage with absolute paths for easy access

Example: Mermaid code → High-quality PNG/SVG image file

⚙️ Configuration

Basic Setup

- Default storage: {project-root}/generated-diagrams/ - Default Kroki: Uses local Docker Kroki service - Default port: 3000

For advanced configuration, see our Configuration Guide.

📚 Documentation

- Installation Guide - Detailed setup instructions
- Docker Deployment - Container deployment options
- API Reference - Complete tool and resource documentation
- Configuration Guide - Environment variables and customization
- Development Guide - Contributing and development setup
- Architecture - System architecture and design patterns
- Performance & Security - Performance metrics and security features
- Troubleshooting - Common issues and solutions

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Perfect for: LLMs that need to create diagrams but don't know which format to use or how to render them professionally.

Powered by: Kroki - Universal diagram rendering service

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