Rosetta MCP server

Rosetta

AI-powered Excel translation CLI. Translates Excel files while preserving formatting, formulas, and data integrity.

What it does

Rosetta translates all text in your Excel files using Claude AI, without breaking:

• Formulas and calculations
• Formatting (fonts, colors, borders)
• Merged cells and layouts
• Charts and images
• Dropdown menus
• Rich text (bold, italic within cells)

Prerequisites

You need a Claude API key from Anthropic.

1. Go to console.anthropic.com
2. Create an account (or sign in)
3. Go to API Keys and create a new key
4. Copy the key (starts with sk-ant-...)

Note: API usage is billed by Anthropic. See anthropic.com/pricing for current rates. Translating a typical Excel file costs a few cents.

Installation

Install from PyPI:

pip install rosetta-xl

Then set your API key:

# Linux/macOS
export ANTHROPIC_API_KEY=sk-ant-your-key-here

# Windows (Command Prompt)
set ANTHROPIC_API_KEY=sk-ant-your-key-here

# Windows (PowerShell)
$env:ANTHROPIC_API_KEY="sk-ant-your-key-here"

Or create a .env file in your working directory:

ANTHROPIC_API_KEY=sk-ant-your-key-here

Usage

# Translate to French
rosetta input.xlsx -t french

# Translate to Spanish with custom output name
rosetta input.xlsx -t spanish -o translated.xlsx

# Specify source language (auto-detected by default)
rosetta input.xlsx -s english -t german

# Translate only specific sheets
rosetta input.xlsx -t french --sheets "Sheet1" --sheets "Data"

# Add context for better translations (e.g., domain-specific terms)
rosetta input.xlsx -t french -c "Medical terminology document"

Options

Option	Short	Description
--target-lang	-t	Target language (required)
--source-lang	-s	Source language (auto-detect if omitted)
--output	-o	Output file path (default: input_translated.xlsx)
--sheets		Sheets to translate (can repeat, default: all)
--context	-c	Domain context for better accuracy
--batch-size	-b	Cells per API call (default: 50)

Examples

Translate a price list to multiple languages:

rosetta prices.xlsx -t french -o prices_fr.xlsx
rosetta prices.xlsx -t german -o prices_de.xlsx
rosetta prices.xlsx -t spanish -o prices_es.xlsx

Translate a medical form with context:

rosetta patient_form.xlsx -t french -c "Medical intake form with clinical terminology"

Translate only the "Questions" sheet:

rosetta survey.xlsx -t japanese --sheets "Questions"

Troubleshooting

"ANTHROPIC_API_KEY not set"

• Make sure you've exported the key: export ANTHROPIC_API_KEY=sk-ant-...
• Or create a .env file with the key

"Invalid API key"

• Check that your key starts with sk-ant-
• Make sure you copied the full key from console.anthropic.com

"Rate limit exceeded"

• You've hit Anthropic's rate limits. Wait a minute and try again
• Or reduce batch size: rosetta input.xlsx -t french -b 20

How it works

1. Extracts all text cells from your Excel file
2. Sends text to Claude AI for translation (in batches)
3. Writes translations back, preserving all formatting
4. Saves the translated file

Your original file is never modified.

Web App & API

Rosetta also includes a web application and REST API for browser-based translations.

Running the API server

# Install with uv (recommended)
uv sync

# Start the server
uv run uvicorn rosetta.api:app --reload

# Or with pip
pip install -e .
uvicorn rosetta.api:app --reload

The API runs at http://localhost:8000 by default.

Running the frontend

cd frontend
npm install
npm run dev

The frontend runs at http://localhost:5173 and connects to the API.

API Endpoints

Endpoint	Method	Description
/translate	POST	Translate an Excel file (returns file)
/translate-stream	POST	Translate with real-time progress via SSE
/estimate	POST	Get cell count and cost estimate
/sheets	POST	List sheet names in a file
/count	POST	Count translatable cells
/preview	POST	Preview cells that will be translated
/health	GET	Health check

Real-time Progress

The /translate-stream endpoint uses Server-Sent Events (SSE) to stream translation progress in real-time. The frontend automatically falls back to the standard /translate endpoint on networks that don't support SSE (e.g., corporate proxies).

MCP Integration

Rosetta includes MCP (Model Context Protocol) servers for both Claude Desktop and Claude Web.

For Claude Desktop (Local)

Add to your Claude Desktop config (~/Library/Application Support/Claude/claude_desktop_config.json):

{
  "mcpServers": {
    "rosetta": {
      "command": "uv",
      "args": ["run", "--directory", "/path/to/rosetta", "python", "-m", "rosetta.api.mcp"],
      "env": {
        "ANTHROPIC_API_KEY": "your-key-here"
      }
    }
  }
}

Usage: Use local file paths for best results.

Translate ~/Downloads/report.xlsx to French

For Claude Web (Browser)

Note: Claude.ai does not yet support custom MCP servers in the browser (as of January 2026).

Current recommendation: Use the web app for browser-based translations.

See MCP_USAGE.md for detailed instructions.

Requirements

• Python 3.11+
• Anthropic API key

License

MIT