Why MCP?

Imagine you're building an AI assistant for a bank:**

User: "What's my current account balance and how much can I spend on my credit card?"

❌ AI Without MCP:

"I don't have access to your personal banking information. 
You'll need to log into your bank's website or mobile app."

❌ Traditional API Approach:

User has to:
1. Log into banking app
2. Navigate to account section  
3. Check balance
4. Switch to credit card section
5. Check available credit
6. Manually calculate total spending power

✅ AI With MCP (Private Banking Tools):

"Your checking account has $2,450 and your credit card has $3,200 available credit. 
You can spend up to $5,650 total."

Why MCP is Essential for Private Data

The Real MCP Advantage:

• 🔒 Private Data Access: Connect to internal databases, CRM systems, financial records
• 🛠️ Internal Functionality: Trigger company workflows, send emails, create tickets
• 🏢 Business Logic: Access proprietary algorithms, pricing models, customer data
• 🔐 Secure Integration: Controlled access to sensitive company systems

Real-World Examples:

• Banking: "Transfer $500 from savings to checking and pay my credit card bill"
• E-commerce: "Check inventory for iPhone 15, update pricing, and notify warehouse"
• Healthcare: "Schedule appointment with Dr. Smith, check insurance coverage, send reminder"
• CRM: "Find all customers who bought Product X last month and send them upgrade offer"

This Repo

This repository demonstrates how to use MCP to enable real-time currency conversion in an AI assistant, even when the underlying language model doesn't have access to up-to-date exchange rates. It provides a practical example of how AI can leverage external tools via MCP to answer currency-related queries accurately.

Model Context Protocol (MCP) Instead of building complex interfaces, we let AI do the heavy lifting:

• Natural Language: Users just type "Convert 100 USD to Japanese Yen"
• AI Understanding: Claude AI extracts the intent and parameters
• Tool Calling: AI calls our MCP server to get the exchange rate
• Smart Response: AI formats the answer naturally

Example:

User: "I have 50 euros in cash and 200 euros in my bank. How much is that total in dollars?"

AI With MCP:
"Your total is 250 EUR. At current rates, that's approximately $275 USD."

The Bigger Picture

This project demonstrates a fundamental shift in how we build applications. Instead of complex UIs and rigid APIs, we're moving toward AI-native interfaces that understand natural language and context.

Hono.js Currency Exchange MCP Service

A Node.js service built with Hono.js that provides a single API endpoint for currency exchange queries. The service integrates with an MCP (Model Context Protocol) server to provide real-time currency exchange rates and uses Claude AI to interpret user requests.

https://github.com/user-attachments/assets/aa88ab4e-511a-4ece-9881-5bf156570b38

🏗️ Architecture

User Request → Hono API → Claude AI → MCP Server → Freecurrencyapi → Response

Flow Details:

1. User sends a prompt like "What is 100 USD in EUR?"
2. Hono API receives the request
3. Claude AI interprets the request and calls the get_exchange_rate tool
4. MCP server fetches the exchange rate from Freecurrencyapi
5. Claude AI calculates the result and responds with the conversion

Setup

1. Install Dependencies

npm install

2. Environment Variables

Copy the example environment file and fill in your API keys:

cp env.example .env

Edit .env with your actual API keys:

ANTHROPIC_API_KEY=your_anthropic_api_key_here
CURRENCY_API_KEY=your_freecurrency_api_key_here
PORT=8000

3. Get API Keys

• Anthropic API Key: Get from Anthropic Console
• Freecurrencyapi Key: Get from Freecurrencyapi

4. Run the Service

Development mode (with auto-reload):

npm run dev

Production mode:

npm start

The service will start on port 8000 (or the port specified in your .env file).

API Usage

POST /api/chat

Send a natural language prompt about currency exchange.

Request:

{
  "prompt": "Is ¥10,000 (Japanese Yen) enough to buy a $60 USD video game?"
}

Response:

{
  "response": "Yes, ¥10,000 JPY is enough to buy a $60 USD video game. When converted, ¥10,000 JPY is worth approximately $65.83 USD, which gives you about $5.83 USD in change after buying the $60 game.",
}

Example Queries

• "What is 100 USD in EUR?"
• "I have 5 euros in cash and 20 euros in my bank—what's the total in USD?"
• "If I get paid 3500 GBP per month, how much is that in Canadian dollars?"
• "Is ¥10,000 (Japanese Yen) enough to buy a $60 USD video game?"
• "I want to convert 150 Swiss Francs and 80 USD into euros, how much do I get?"

Available Scripts

• npm run dev - Start development server with auto-reload
• npm start - Start production server
• npm run mcp-server - Run MCP server standalone (for testing)

MCP Server

The MCP server (mcp-server.ts) provides a single tool:

• get_exchange_rate: Get exchange rate between currencies
  • Parameters: from_currency, to_currency, amount (optional)
  • Returns: Exchange rate and converted amount

License

ISC