SpellChecker MCP Server

A fast, multilingual Model Context Protocol (MCP) server that provides spell-checking capabilities to Large Language Models. This server enables LLMs to check spelling in text, files, and entire projects with syntax-aware parsing for code files.

Features

• Multi-language support: 15+ languages including English, Spanish, French, German, Portuguese, Italian, Dutch, Polish, Russian, Ukrainian, Swedish, Danish, and Norwegian

• Syntax-aware checking: Intelligently checks only comments, strings, and documentation in code files

• File and folder scanning: Check individual files or entire project directories

• Modular language activation: Enable only the languages you need

• Fast spell checking: Powered by nspell for efficient processing

• Custom dictionary management: Add words to personal dictionaries

• Smart code parsing: Understands HTML, JavaScript, TypeScript, Python, and more

• MCP-compliant: Works with any MCP-compatible client

Related MCP server: Translations MCP Server

Installation

As an MCP Server

1. Clone the repository:

git clone https://github.com/yourusername/spellchecker-mcp-server.git
cd spellchecker-mcp-server

2. Install dependencies and build:

yarn install
yarn build

The post-install script will automatically download the required dictionary files.

Using with Claude Desktop

Add the server to your Claude Desktop configuration file:

macOS: ~/Library/Application Support/Claude/claude_desktop_config.json Windows: %APPDATA%\Claude\claude_desktop_config.json

{
  "mcpServers": {
    "spellchecker": {
      "command": "node",
      "args": ["/path/to/spellchecker-mcp-server/dist/index.js"],
      "env": {
        "SPELLCHECKER_LANGUAGES": "en-US,es,fr"
      }
    }
  }
}

Configuring Languages

You can configure which languages to enable in three ways:

1. Environment variable (recommended for Claude Desktop):

   SPELLCHECKER_LANGUAGES="en-US,es,fr" node dist/index.js

2. Configuration file:

   SPELLCHECKER_CONFIG="/path/to/spellchecker.config.json" node dist/index.js

3. Edit the default in src/config.ts before building

Using with Other MCP Clients

The server runs on stdio and can be integrated with any MCP-compatible client:

node /path/to/spellchecker-mcp-server/dist/index.js

Available Tools

check_spelling

Checks text for spelling errors and returns misspellings with suggestions.

Parameters:

• text (required): The text to check

• language (optional): Language code (default: "en-US")

• includeLineNumbers (optional): Include line/column positions (default: false)

Example:

{
  "text": "This is a tset of the speling checker",
  "language": "en-US",
  "includeLineNumbers": true
}

is_correct

Checks if a single word is spelled correctly.

Parameters:

• word (required): The word to check

• language (optional): Language code (default: "en-US")

get_suggestions

Gets spelling suggestions for a word.

Parameters:

• word (required): The word to get suggestions for

• language (optional): Language code (default: "en-US")

• limit (optional): Maximum suggestions to return (default: 5)

add_to_dictionary

Adds a word to the personal dictionary for a language.

Parameters:

• word (required): The word to add

• language (optional): Language code (default: "en-US")

list_languages

Lists all available languages for spell checking.

check_file

Checks spelling in a single file with syntax-aware parsing.

Parameters:

• filePath (required): Path to the file to check

• language (optional): Language code (default: "en-US")

• syntaxAware (optional): Enable syntax-aware parsing (default: true)

Example:

{
  "filePath": "/path/to/app.tsx",
  "language": "en-US",
  "syntaxAware": true
}

check_folder

Checks spelling in all files within a folder.

Parameters:

• folderPath (required): Path to the folder to check

• language (optional): Language code (default: "en-US")

• recursive (optional): Check subfolders (default: true)

• fileTypes (optional): Array of file extensions to check

• syntaxAware (optional): Enable syntax-aware parsing (default: true)

Example:

{
  "folderPath": "/path/to/project",
  "language": "en-US",
  "recursive": true,
  "fileTypes": [".js", ".tsx", ".md"],
  "syntaxAware": true
}

Supported Languages

The server supports 15+ languages. Enable only what you need:

• en-US - English (United States)

• en-GB - English (United Kingdom)

• es - Spanish

• fr - French

• de - German

• pt - Portuguese

• pt-BR - Portuguese (Brazil)

• it - Italian

• nl - Dutch

• pl - Polish

• ru - Russian

• uk - Ukrainian

• sv - Swedish

• da - Danish

• nb - Norwegian Bokmål

Syntax-Aware Features

When syntaxAware is enabled, the spell checker intelligently parses:

• Comments: Single-line and multi-line comments in all major languages

• String literals: Only checks strings that look like human-readable text

• JSX/TSX content: Text between JSX tags

• Documentation: Docstrings, JSDoc comments, etc.

• Markdown: Ignores code blocks and inline code

• HTML/XML: Checks text content and comments

The checker automatically ignores:

• Variable names and identifiers

• Programming keywords

• URLs and file paths

• Hex colors and numbers

• Code within backticks in Markdown

Development

Prerequisites

• Node.js >= 16.0.0

• Yarn package manager

Setup

# Install dependencies
yarn install

# Run in development mode
yarn dev

# Build for production
yarn build

# Type check
yarn typecheck

Using Just Commands

If you have just installed:

# Show available commands
just

# Fresh install
just fresh

# Run development server
just dev

# Update dictionaries
just dictionaries

Architecture

The server uses:

• @modelcontextprotocol/sdk: MCP protocol implementation

• nspell: Hunspell-compatible spell checker

• glob: File pattern matching for directory scanning

• TypeScript: Type-safe development

• Dictionary files: From the wooorm/dictionaries project

Configuration File

Create a spellchecker.config.json file:

{
  "languages": ["en-US", "es", "fr"],
  "defaultLanguage": "en-US",
  "scanOptions": {
    "syntaxAware": true,
    "recursive": true,
    "fileTypes": [
      ".txt", ".md", ".mdx",
      ".js", ".jsx", ".ts", ".tsx",
      ".py", ".java", ".go"
    ],
    "ignorePaths": [
      "node_modules",
      ".git",
      "dist",
      "build"
    ]
  }
}

Contributing

Contributions are welcome! Please feel free to submit a Pull Request.

1. Fork the repository

2. Create your feature branch (git checkout -b feature/AmazingFeature)

3. Commit your changes (git commit -m 'Add some AmazingFeature')

4. Push to the branch (git push origin feature/AmazingFeature)

5. Open a Pull Request

License

This project is licensed under the MIT License - see the LICENSE file for details.

Acknowledgments

• Dictionary files from wooorm/dictionaries

• Built on the Model Context Protocol

Troubleshooting

Dictionaries not loading

If you see "No dictionaries loaded" error:

yarn run postinstall
# or
just dictionaries

Server not starting

Ensure you've built the project:

yarn build

Language not available

Check available languages with the list_languages tool or ensure the dictionary files exist in the dictionaries/ folder.