MCP Avantage

Instructions

Implementation Reference

• src/index.ts:567-581 (registration)

  Registers the MCP tool 'economicIndicators_realGDPPerCapita' with description, input schema reference, and inline execute handler that delegates to the generic executeAvantageTool and AVantage library method.

  server.addTool({
    name: "economicIndicators_realGDPPerCapita",
    description: "Retrieves US Real GDP per Capita data.",
    parameters: schemas.EconomicIndicatorsDataTypeParamSchema,
    execute: (
      args,
      context // Let type be inferred
    ) =>
      executeAvantageTool(
        "economicIndicators_realGDPPerCapita",
        args,
        context,
        (av, params) => av.economicIndicators.realGDPPerCapita(params)
      ),
  });

• src/index.ts:38-115 (handler)

  Generic async handler function shared by all tools. Manages authentication, AVantage instance via resourceManager, executes the library method (av.economicIndicators.realGDPPerCapita for this tool), handles errors, and returns JSON stringified data.

  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}`
      );
    }
  }

• src/schemas.ts:124-127 (schema)

  Zod input validation schema for the tool. Accepts optional 'datatype' parameter (json or csv). Shared with other economic indicators.

  export const EconomicIndicatorsDataTypeParamSchema = z.object({
    datatype: DatatypeSchema.default('json').optional(),
  }).describe('Common parameter schema accepting only datatype.')