Frankfurter MCP Server

A Model Context Protocol (MCP) server that provides currency exchange operations using the Frankfurter API. This server enables LLMs to perform real-time currency conversions, query historical exchange rates, analyze time series data, and discover available currencies.

Features

• Currency Conversion: Convert amounts between currencies using current or historical exchange rates
• Latest Rates: Get the most recent exchange rates (updated daily at 4 PM CET)
• Historical Rates: Query exchange rates for any date since 1999-01-04
• Time Series Analysis: Retrieve exchange rate trends over date ranges
• Currency Discovery: List all 30+ supported currencies with full names
• Dual Output Formats: Both JSON (structured) and Markdown (human-readable) response formats
• Error Handling: Clear, actionable error messages to guide correct usage
• Context-Efficient: Automatic truncation for large responses to protect LLM context windows

Installation

Prerequisites

• Node.js >= 18
• npm or yarn

Option 1: Install from npm (Recommended)

# Install globally
npm install -g frankfurter-mcp-server

# Or use with npx (no installation required)
npx frankfurter-mcp-server

Option 2: Install from source

# Clone the repository
git clone https://github.com/DrTrips-Comp/frankfurter-mcp-server.git
cd frankfurter-mcp-server

# Install dependencies
npm install

# Build the TypeScript code
npm run build

# Test the server
node dist/index.js

Configuration

Add this server to your Claude Desktop configuration:

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

Using npx (Recommended)

{
  "mcpServers": {
    "frankfurter": {
      "command": "npx",
      "args": ["-y", "frankfurter-mcp-server"]
    }
  }
}

Using global installation

{
  "mcpServers": {
    "frankfurter": {
      "command": "frankfurter-mcp-server"
    }
  }
}

Using local installation

{
  "mcpServers": {
    "frankfurter": {
      "command": "node",
      "args": ["/absolute/path/to/frankfurter-mcp-server/dist/index.js"]
    }
  }
}

Available Tools

1. frankfurter_convert_currency

Convert an amount from one currency to another.

Parameters:

• from (required): Source currency code (3-letter ISO, e.g., "EUR", "USD")
• to (required): Target currency code (3-letter ISO)
• amount (required): Amount to convert (positive number)
• date (optional): Historical date in YYYY-MM-DD format
• response_format (optional): "json" or "markdown" (default: "markdown")

Example:

{
  "from": "EUR",
  "to": "USD",
  "amount": 100,
  "response_format": "markdown"
}

2. frankfurter_get_latest_rates

Get the latest exchange rates for a base currency.

Parameters:

• base (optional): Base currency code (default: "EUR")
• symbols (optional): Array of target currency codes to filter results
• response_format (optional): "json" or "markdown" (default: "markdown")

Example:

{
  "base": "USD",
  "symbols": ["EUR", "GBP", "JPY"],
  "response_format": "json"
}

3. frankfurter_get_historical_rates

Get exchange rates for a specific historical date.

Parameters:

• date (required): Historical date in YYYY-MM-DD format (>= 1999-01-04)
• base (optional): Base currency code (default: "EUR")
• symbols (optional): Array of target currency codes to filter results
• response_format (optional): "json" or "markdown" (default: "markdown")

Example:

{
  "date": "2020-01-15",
  "base": "EUR",
  "symbols": ["USD", "GBP"],
  "response_format": "markdown"
}

4. frankfurter_get_time_series

Get exchange rate time series data over a date range.

Parameters:

• start_date (required): Start date in YYYY-MM-DD format (>= 1999-01-04)
• end_date (required): End date in YYYY-MM-DD format (must be after start_date)
• base (optional): Base currency code (default: "EUR")
• symbols (optional): Array of target currency codes (recommended: 2-5 currencies)
• response_format (optional): "json" or "markdown" (default: "markdown")

Example:

{
  "start_date": "2024-01-01",
  "end_date": "2024-01-31",
  "base": "EUR",
  "symbols": ["USD", "GBP"],
  "response_format": "markdown"
}

Note: Large date ranges may be truncated. For best results, query smaller ranges (1-3 months).

5. frankfurter_list_currencies

List all available currencies supported by the Frankfurter API.

Parameters:

• response_format (optional): "json" or "markdown" (default: "markdown")

Example:

{
  "response_format": "markdown"
}

Data Source

This server uses the Frankfurter API, which provides:

• Exchange rates from the European Central Bank (ECB)
• Daily updates at 4 PM CET
• Historical data from 1999-01-04 onwards
• 30+ currency pairs
• Free access with no API key required

Design Philosophy

This MCP server follows agent-centric design principles:

• Workflow-Oriented Tools: Tools complete useful tasks, not just API wrappers
• Context-Efficient: Optimized response formats to minimize token usage
• Actionable Errors: Clear guidance to help LLMs correct mistakes
• Natural Task Flow: Tool names reflect how humans think about currency operations

Limitations

• Rates update once daily (not real-time tick-by-tick data)
• No authentication required (public API)
• Character limit of 25,000 per response (with automatic truncation)
• Weekend/holiday dates return nearest business day rates
• All dates are in UTC timezone

Troubleshooting

Server won't start

• Verify Node.js >= 18 is installed: node --version
• Ensure dependencies are installed: npm install
• Check build completed successfully: npm run build

API timeout errors

• The Frankfurter API has a 10-second timeout
• Check your internet connection
• Try the request again after a moment

Currency code not found

• Use frankfurter_list_currencies to see all valid currency codes
• Ensure codes are 3 letters and uppercase (automatically converted)

Large time series truncated

• Reduce the date range (e.g., query 1 month instead of 1 year)
• Use the symbols parameter to filter specific currencies
• Query multiple smaller ranges instead of one large range

Development

Project Structure

src/
  index.ts              # Main server and tool handlers
  constants.ts          # Configuration constants
  types.ts              # TypeScript type definitions
  services/
    frankfurter-client.ts  # API client with error handling
    formatter.ts           # Response formatting utilities

Scripts

npm run build    # Compile TypeScript to JavaScript
npm run dev      # Watch mode for development
npm run start    # Run the compiled server

Testing Locally

# Build the project
npm run build

# Run the server
node dist/index.ts

# The server will run on stdio, waiting for MCP protocol messages

License

MIT

Contributing

Contributions are welcome! Please follow these guidelines:

1. Maintain the agent-centric design philosophy
2. Add comprehensive error handling with actionable messages
3. Update documentation for any new features
4. Test with the Frankfurter API before submitting

Links

• Frankfurter API Documentation
• Model Context Protocol
• European Central Bank

Support

For issues or questions:

1. Check the Troubleshooting section above
2. Verify the Frankfurter API status
3. Review the tool descriptions in Claude Desktop
4. Open an issue in this repository