Currency Converter MCP

Implementation Reference

• src/tools/get_historical_rates.ts:32-76 (handler)

  The main tool handler function that fetches historical exchange rates from the Frankfurter API, handles parameters, makes the fetch request, and returns formatted response or error.

  export async function getHistoricalRates(
  	input: GetHistoricalRatesInput,
  ): Promise<ToolResponse> {
  	const { date, base, symbols } = input;
  
  	try {
  		const params = new URLSearchParams();
  		if (base) params.append("base", base.toUpperCase());
  		if (symbols) params.append("symbols", symbols.toUpperCase());
  
  		const url = `${FRANKFURTER_API_BASE}/${date}${params.toString() ? `?${params.toString()}` : ""}`;
  		const response = await fetch(url);
  
  		if (!response.ok) {
  			return {
  				content: [
  					{
  						type: "text",
  						text: `Error: Unable to fetch historical rates. Status: ${response.status}`,
  					},
  				],
  			};
  		}
  
  		const data = (await response.json()) as ExchangeRateResponse;
  
  		return {
  			content: [
  				{
  					type: "text",
  					text: JSON.stringify(data),
  				},
  			],
  		};
  	} catch (error) {
  		return {
  			content: [
  				{
  					type: "text",
  					text: `Error: Failed to fetch historical rates - ${error instanceof Error ? error.message : "Unknown error"}`,
  				},
  			],
  		};
  	}
  }

• src/tools/get_historical_rates.ts:8-22 (schema)

  Input schema using Zod for validating the date (YYYY-MM-DD), optional base currency (3-letter code), and optional symbols (comma-separated currencies).

  export const getHistoricalRatesSchema = {
  	date: z
  		.string()
  		.regex(/^\d{4}-\d{2}-\d{2}$/)
  		.describe("Date in YYYY-MM-DD format"),
  	base: z
  		.string()
  		.length(3)
  		.optional()
  		.describe("Base currency code (default: EUR)"),
  	symbols: z
  		.string()
  		.optional()
  		.describe("Comma-separated currency codes to limit results"),
  };

• src/index.ts:37-41 (registration)

  Registration of the 'get_historical_rates' tool in the MCP server using the schema and handler function.

  this.server.tool(
    "get_historical_rates",
    getHistoricalRatesSchema,
    async (input) => getHistoricalRates(input),
  );