Currency Converter MCP

Implementation Reference

• src/tools/get_currencies.ts:13-51 (handler)

  The handler function that fetches the list of available currencies from the Frankfurter API endpoint and returns the data as a JSON string in a ToolResponse format, or an error message if the fetch fails.

  export async function getCurrencies(
  	_input: GetCurrenciesInput,
  ): Promise<ToolResponse> {
  	try {
  		const url = `${FRANKFURTER_API_BASE}/currencies`;
  		const response = await fetch(url);
  
  		if (!response.ok) {
  			return {
  				content: [
  					{
  						type: "text",
  						text: `Error: Unable to fetch currencies. Status: ${response.status}`,
  					},
  				],
  			};
  		}
  
  		const data = (await response.json()) as CurrenciesResponse;
  
  		return {
  			content: [
  				{
  					type: "text",
  					text: JSON.stringify(data),
  				},
  			],
  		};
  	} catch (error) {
  		return {
  			content: [
  				{
  					type: "text",
  					text: `Error: Failed to fetch currencies - ${error instanceof Error ? error.message : "Unknown error"}`,
  				},
  			],
  		};
  	}
  }

• src/tools/get_currencies.ts:7-11 (schema)

  The schema definition (empty object indicating no input parameters) and TypeScript types for input (empty record) and output (CurrenciesResponse).

  export const getCurrenciesSchema = {};
  
  export type GetCurrenciesInput = Record<string, never>;
  
  export type GetCurrenciesOutput = CurrenciesResponse;

• src/index.ts:33-35 (registration)

  The registration of the "get_currencies" tool on the MCP server, providing the schema and handler function.

  this.server.tool("get_currencies", getCurrenciesSchema, async (input) =>
    getCurrencies(input),
  );