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Mermaid Validator: Effortless Validation & Flawless Rendering - MCP Implementation

Mermaid Validator: Effortless Validation & Flawless Rendering

Ensure rock-solid Mermaid diagrams with our Model Context Protocol server—effortless validation, flawless rendering, no errors, just perfect results. Your workflow’s new MVP.

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About Mermaid Validator

What is Mermaid Validator: Effortless Validation & Flawless Rendering?

Mermaid Validator is a Model Context Protocol (MCP) server designed to simplify Mermaid diagram validation and rendering. By integrating with MCP-compatible clients, it enables AI tools like LLMs to process Mermaid syntax seamlessly. The solution combines robust validation with real-time SVG generation, ensuring developers and designers can instantly verify diagram accuracy while obtaining high-quality visual outputs.

How to Use Mermaid Validator: Effortless Validation & Flawless Rendering?

Integration is straightforward: configure your MCP client by adding the server definition to your configuration file:


    {
      "mcpServers": {
        "mermaid-validator": {
          "command": "npx",
          "args": ["-y", "@rtuin/mcp-mermaid-validator"]
        }
      }
    }
  

After setup, execute standard MCP workflows to validate diagrams and retrieve rendered SVGs. Development workflows are supported via npm scripts for building, linting, and watching code changes.

Mermaid Validator Features

Key Features of Mermaid Validator: Effortless Validation & Flawless Rendering?

  • MCP Standard Compliance: Leverages the Model Context Protocol for universal tool interoperability
  • Isolated Execution: Uses child processes to safely execute Mermaid CLI operations
  • Rich Error Feedback: Provides detailed syntax errors alongside validation status
  • TypeScript Foundation: Built with strict typing and linter/formatter integration
  • Base64 SVG Output: Returns rendered diagrams in a format immediately usable in web contexts

Use Cases of Mermaid Validator: Effortless Validation & Flawless Rendering?

Primary scenarios include:

  • Real-time diagram validation in IDE plugins
  • Automated documentation generation pipelines
  • AI-driven diagram correction tools
  • Collaborative diagramming platforms requiring syntax verification
  • Continuous integration workflows for technical documentation

Mermaid Validator FAQ

FAQ from Mermaid Validator: Effortless Validation & Flawless Rendering?

How does error handling work?

Uses a multi-layered approach to distinguish between syntax errors and system failures, returning structured error messages with diagnostic details.

Can I customize the rendering output?

Currently supports SVG output only, but future versions may add format flexibility through configuration options.

What about performance?

Optimized for quick validation cycles using lightweight CLI interactions, with parallel processing capabilities for batch operations.

Is it open-source?

Yes, built on industry-standard tools with transparent code structure available on GitHub.

Content

MCP Server: Mermaid Validator

A Model Context Protocol server that validates and renders Mermaid diagrams. This server enables LLMs to validate and render Mermaid diagrams.

Usage

Quick Start

You can configure your MCP client to use the Mermaid Validator by adding it to your mcp servers file:

{
  "mcpServers": {
    "mermaid-validator": {
      "command": "npx",
      "args": [
        "-y",
        "@rtuin/mcp-mermaid-validator"
      ]
    }
  }
}

Architecture

High-Level Architecture

This project is structured as a simple TypeScript Node.js application that:

  1. Main Application : A Node.js service that validates Mermaid diagrams and returns rendered SVG output
  2. MCP Integration : Uses the Model Context Protocol SDK to expose functionality to MCP-compatible clients
  3. Mermaid CLI Integration : Leverages the Mermaid CLI tool to perform diagram validation and rendering

Code Structure

mcp-mermaid-validator/
├── dist/                   # Compiled JavaScript output
│   └── main.js             # Compiled main application
├── src/                    # TypeScript source code
│   └── main.ts             # Main application entry point
├── node_modules/           # Dependencies
├── package.json            # Project dependencies and scripts
├── package-lock.json       # Dependency lock file
├── tsconfig.json           # TypeScript configuration
├── eslint.config.js        # ESLint configuration
├── .prettierrc             # Prettier configuration
└── README.md               # Project documentation

Component Functionality

MCP Server (Main Component)

The core functionality is implemented in src/main.ts. This component:

  1. Creates an MCP server instance
  2. Registers a validateMermaid tool that accepts Mermaid diagram syntax
  3. Uses the Mermaid CLI to validate and render diagrams
  4. Returns validation results and rendered SVG (if valid)
  5. Handles error cases with appropriate error messages

Data Flow

  1. Input : Mermaid diagram syntax as a string
  2. Processing :
    * The diagram is passed to the Mermaid CLI via stdin
    * The CLI validates the syntax and renders an SVG if valid
    * Output and errors are captured from stdout/stderr
  3. Output :
    * Success: Text confirmation + rendered SVG as base64-encoded image
    * Failure: Error message with details about the validation failure

Dependencies

External Libraries

  • @modelcontextprotocol/sdk : SDK for implementing Model Context Protocol
  • @mermaid-js/mermaid-cli : CLI tool for validating and rendering Mermaid diagrams
  • zod : Schema validation library for TypeScript

Development Dependencies

  • typescript : TypeScript compiler
  • eslint : Linting utility
  • prettier : Code formatting

API Specification

validateMermaid Tool

Purpose : Validates a Mermaid diagram and returns the rendered SVG if valid

Parameters :

  • diagram (string): The Mermaid diagram syntax to validate

Return Value :

  • Success:

    {
    

    content: [
    {
    type: "text",
    text: "Mermaid diagram is valid"
    },
    {
    type: "image",
    data: string, // Base64-encoded SVG
    mimeType: "image/svg+xml"
    }
    ]
    }

  • Failure:

    {
    

    content: [
    {
    type: "text",
    text: "Mermaid diagram is invalid"
    },
    {
    type: "text",
    text: string // Error message
    },
    {
    type: "text",
    text: string // Detailed error output (if available)
    }
    ]
    }

Technical Decisions

  1. MCP Integration : The project uses the Model Context Protocol to standardize the interface for AI tools, allowing seamless integration with compatible clients.

  2. Child Process Approach : The implementation uses Node.js child processes to interact with the Mermaid CLI, which provides:

* Isolation between the main application and the rendering process
* Ability to capture detailed error information
* Proper handling of the rendering pipeline
  1. Error Handling Strategy : The implementation uses a nested try-catch structure to:
* Distinguish between validation errors (invalid diagram syntax) and system errors
* Provide detailed error information to help users fix their diagrams
* Ensure the service remains stable even when processing invalid input
  1. Simple Project Structure : The project uses a straightforward TypeScript project structure for:
* Easy maintenance and understanding
* Direct dependency management
* Simplified build process

Build and Execution

The application can be built and run using npm scripts:

# Install dependencies
npm install

# Build the application
npm run build

# Run locally (for development)
npx @modelcontextprotocol/inspector node dist/main.js

# Format code
npm run format

# Lint code
npm run lint

# Watch for changes (development)
npm run watch

The application runs as an MCP server that communicates via standard input/output, making it suitable for integration with MCP-compatible clients.

Release

To release a new version, the following steps in order:

  • npm run build
  • npm run bump
  • npm run changelog
  • npm publish --access public

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