DeepL MCP Server

An MCP (Model Context Protocol) server providing high-quality translation capabilities via the DeepL API.

Features

This server provides 5 tools for working with DeepL:

| Tool | Description | Required Params | |------|-------------|-----------------| | translate_text | Translate text with formality control, context, and glossary support | text, target_lang | | rephrase_text | Improve text clarity and style using DeepL Write (Pro only) | text | | get_source_languages | List all available source languages | — | | get_target_languages | List all target languages with formality support info | — | | get_usage | Get API usage statistics (character count and limits) | — |

Translation Features

• Formality control — Adjust tone for formal/informal contexts (supported languages: DE, FR, IT, ES, NL, PL, PT, JA, RU)
• Context parameter — Provide additional context for better accuracy (not billed)
• Glossary support — Use custom terminology with glossary IDs
• Batch translation — Translate multiple texts in a single request
• Preserve formatting — Keep original text formatting
• Sentence splitting control — Control how sentences are split

API Type Auto-Detection

The server automatically detects whether you're using the Free or Pro API based on your key format:

• Keys ending in :fx → Free API (api-free.deepl.com)
• Other keys → Pro API (api.deepl.com)

Prerequisites

• Node.js 18+ (including Node.js 25)
• DeepL API Key — Sign up here (Free tier available)

Quick Start

1. Clone and Build

git clone https://github.com/watchdealer-pavel/deepl-mcp-server.git
cd deepl-mcp-server
npm install

2. Configure Your MCP Client

Add to your MCP client configuration:

Claude Desktop (~/Library/Application Support/Claude/claude_desktop_config.json):

{
  "mcpServers": {
    "deepl": {
      "command": "node",
      "args": ["/path/to/deepl-mcp-server/build/index.js"],
      "env": {
        "DEEPL_API_KEY": "your-api-key-here"
      }
    }
  }
}

Claude Code (.mcp.json in your project):

{
  "mcpServers": {
    "deepl": {
      "command": "node",
      "args": ["/path/to/deepl-mcp-server/build/index.js"],
      "env": {
        "DEEPL_API_KEY": "your-api-key-here"
      }
    }
  }
}

3. Restart Your MCP Client

Restart Claude Desktop or Claude Code to load the server.

Usage Examples

Basic Translation

{
  "text": "Hello, how are you?",
  "target_lang": "DE"
}

Formal Translation with Context

{
  "text": "Thanks for your help!",
  "target_lang": "DE",
  "formality": "more",
  "context": "Business email to a client"
}

Batch Translation

{
  "text": ["Hello", "Goodbye", "Thank you"],
  "target_lang": "FR"
}

Check API Usage

Use get_usage to see your current quota:

{
  "character_count": 12500,
  "character_limit": 500000,
  "characters_remaining": 487500,
  "percent_used": "2.50%",
  "api_type": "Free"
}

Supported Languages

Source Languages (auto-detected if omitted)

AR, BG, CS, DA, DE, EL, EN, ES, ET, FI, FR, HU, ID, IT, JA, KO, LT, LV, NB, NL, PL, PT, RO, RU, SK, SL, SV, TR, UK, ZH

Target Languages

All source languages plus regional variants:

• EN-GB — British English
• EN-US — American English
• PT-BR — Brazilian Portuguese
• PT-PT — European Portuguese
• ZH-HANS — Simplified Chinese
• ZH-HANT — Traditional Chinese

Use get_target_languages for a complete list with formality support indicators.

Error Handling

The server handles common API errors:

• 400 — Invalid parameters
• 401/403 — Authentication failed
• 429 — Rate limit exceeded
• 456 — Quota exceeded

Development

# Watch mode (auto-rebuild)
npm run watch

# Manual build
npm run build

# Run the server
npm start

# Test with MCP Inspector
npm run inspector

License

MIT License — see LICENSE file.

Links

• DeepL API Documentation
• DeepL Pro API — Sign up for API access
• Model Context Protocol — MCP documentation