MCP Avantage

Instructions

Implementation Reference

• src/index.ts:723-734 (registration)

  Registers the 'forex_intraday' MCP tool with the server, defining its name, description, input schema, and execution handler that delegates to executeAvantageTool calling av.forex.intraday.

  server.addTool({
    name: "forex_intraday",
    description: "Fetches intraday time series data for a Forex pair.",
    parameters: schemas.ForexIntradayParamsSchema,
    execute: (
      args,
      context // Let type be inferred
    ) =>
      executeAvantageTool("forex_intraday", args, context, (av, params) =>
        av.forex.intraday(params)
      ),
  });

• src/schemas.ts:150-156 (schema)

  Zod schema defining input parameters for the forex_intraday tool: from_symbol, to_symbol, interval, outputsize, datatype.

  export const ForexIntradayParamsSchema = z.object({
    from_symbol: z.string().describe('The currency symbol to convert from (e.g., "EUR").'),
    to_symbol: z.string().describe('The currency symbol to convert to (e.g., "USD").'),
    interval: MinuteIntervalsSchema,
    outputsize: OutputSizeSchema.default('compact').optional(),
    datatype: DatatypeSchema.default('json').optional(),
  }).describe('Parameters for fetching intraday Forex time series data.')

• src/index.ts:727-733 (handler)

  The execute handler function for the tool, which invokes the shared executeAvantageTool helper with the specific Alpha Vantage forex.intraday method.

  execute: (
    args,
    context // Let type be inferred
  ) =>
    executeAvantageTool("forex_intraday", args, context, (av, params) =>
      av.forex.intraday(params)
    ),

• src/index.ts:38-115 (helper)

  Shared helper function that manages Alpha Vantage API key, client instance via resource manager, executes the provided method, handles errors, and returns JSON stringified data. Used by all tools including forex_intraday.

  async function executeAvantageTool<TArgs, TResult>(
    toolName: string,
    args: TArgs,
    context: Context<Record<string, unknown> | undefined>, // Use the imported Context type directly
    avantageMethod: (
      av: AVantage,
      args: TArgs
    ) => Promise<{ error?: boolean; reason?: string; data?: TResult }>
  ): Promise<string> {
    logger.info(`Executing '${toolName}' tool for request ID: ${context}`);
    logger.debug(`Args for ${toolName}: ${JSON.stringify(args)}`);
  
    // --- Authentication & Resource Management ---
    // Access extraArgs safely - it might be null or undefined
    const extraArgsApiKey = context.extraArgs?.apiKey as string | undefined;
    const apiKey = extraArgsApiKey || config.apiKey;
  
    if (!apiKey) {
      logger.error(`'${toolName}' failed: Alpha Vantage API key missing.`);
      throw new UserError(apiKeyErrorMessage);
    }
    logger.debug(
      `Using AV API key (source: ${extraArgsApiKey ? "extraArgs" : "environment"}) for ${toolName}`
    );
  
    try {
      // Get or create AVantage instance managed by ResourceManager
      const av = await resourceManager.getResource<AVantage>(
        apiKey, // Cache key is the resolved API key
        "avantage_client", // Type identifier for logging
        async (key) => {
          // Factory Function
          logger.info(
            `Creating new AVantage instance for key ending ...${key.slice(-4)}`
          );
          // AVantage library reads AV_PREMIUM from process.env internally
          return new AVantage(key);
        },
        async (avInstance) => {
          // Cleanup Function (no-op needed for AVantage)
          logger.debug(`Destroying AVantage instance (no-op)`);
        }
      );
  
      // --- Library Call ---
      const result = await avantageMethod(av, args);
  
      // --- Response Handling ---
      if (result.error) {
        logger.warn(
          `'${toolName}' failed. Reason from avantage: ${result.reason}`
        );
        throw new UserError(result.reason || `Tool '${toolName}' failed.`);
      }
  
      if (result.data === undefined || result.data === null) {
        logger.warn(`'${toolName}' completed successfully but returned no data.`);
        return "null"; // Return string "null" for empty data
      }
  
      logger.info(`'${toolName}' completed successfully.`);
      // Stringify the data part of the response
      return JSON.stringify(result.data);
    } catch (error: any) {
      logger.error(
        `Error during execution of '${toolName}': ${error.message}`,
        error
      );
      // If it's already a UserError, rethrow it
      if (error instanceof UserError) {
        throw error;
      }
      // Otherwise, wrap it in a UserError
      throw new UserError(
        `An unexpected error occurred while executing tool '${toolName}': ${error.message}`
      );
    }
  }