npm package: @iflow-mcp/tohachan-diagram-bridge-mcp
Description: A "bridge" MCP server with a unique Prompt+Tool design that helps LLMs seamlessly generate and render diagrams. Powered by Kroki to support dozens of formats.
Author: Anton An
Latest version: 1.0.6

# Diagram Bridge MCP Server

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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

![Demo](docs/diagram-briedge-mcp.gif)

##  Quick Start

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

2. **Install and build**:
```bash
git clone git@github.com:tohachan/diagram-bridge-mcp.git
cd diagram-bridge-mcp
npm install && npm run build
```

3. **Configure ports (optional)**:
```bash
# Copy and edit environment file to customize ports
cp .env.example .env
# Edit .env to set PORT and KROKI_PORT as needed

# Or set environment variables directly:
export PORT=4000        # MCP Server port (default: 3000)
export KROKI_PORT=9000  # Kroki service port (default: 8000)
```

4. **Start services**:
```bash
# Option 1: Interactive port configuration
./scripts/start-with-ports.sh

# Option 2: Default ports (3000 for MCP, 8000 for Kroki)
docker-compose up --build

# Option 3: Custom ports via environment variables
PORT=4000 KROKI_PORT=9000 docker-compose up --build
```

5. **Add to Cursor** (or any MCP client):

For **direct local use** (without Docker):
```json
{
  "mcpServers": {
    "diagram-bridge-mcp": {
      "command": "node",
      "args": ["/path/to/diagram-bridge-mcp/dist/index.js"],
      "enabled": true
    }
  }
}
```

For **Docker-based setup** (recommended):
```json
{
  "mcpServers": {
    "diagram-bridge-mcp": {
      "command": "docker",
      "args": [
        "exec", 
        "-i", 
        "diagram-bridge-mcp", 
        "node", 
        "dist/index.js"
      ],
      "enabled": true
    }
  }
}
```

**Note**: The MCP protocol uses STDIO communication. The HTTP endpoints (`:3000/health`) are only for Docker monitoring, not for MCP client connections.

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](docs/examples.md)**

## 🛠️ 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 ports**: MCP Server (3000), Kroki (8000)

### Port Configuration
The server automatically configures ports based on environment variables:

- **External Port** (`PORT`): The port exposed by Docker container (default: 3000)
- **Kroki Port** (`KROKI_PORT`): The port for Kroki service (default: 8000)
- **Internal Communication**: Services communicate internally using fixed container ports

```bash
# Interactive configuration (recommended)
./scripts/start-with-ports.sh

# Quick port change
PORT=4000 KROKI_PORT=9000 docker-compose up --build

# Check running services
curl http://localhost:4000/health  # Using your custom PORT
```

**Note**: When running in Docker, the server provides HTTP endpoints for health monitoring at `/health` and service info at `/info`.

For advanced configuration, see our [Configuration Guide](docs/configuration.md).

## 📚 Documentation

- **[Quick Start: Port Configuration](docs/quick-start-ports.md)** - Fast port setup guide
- **[Installation Guide](docs/installation.md)** - Detailed setup instructions
- **[Docker Deployment](docs/docker-deployment.md)** - Container deployment options  
- **[API Reference](docs/api-reference.md)** - Complete tool and resource documentation
- **[Configuration Guide](docs/configuration.md)** - Environment variables and MCP client setup
- **[Development Guide](docs/development.md)** - Contributing and development setup
- **[Architecture](docs/architecture.md)** - System architecture and design patterns
- **[Performance & Security](docs/performance.md)** - Performance metrics and security features  
- **[Troubleshooting](docs/troubleshooting.md)** - Common issues and solutions

---

**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](https://kroki.io) - Universal diagram rendering service

**Made with ❤️**