MCP Avantage

Instructions

Implementation Reference

• src/index.ts:1179-1193 (registration)

  Registration of the MCP tool 'technicalIndicators_htDcperiod' with server.addTool, specifying name, description, parameters schema, and inline execute handler that delegates to executeAvantageTool.

  server.addTool({
    name: "technicalIndicators_htDcperiod",
    description: "Hilbert Transform - Dominant Cycle Period",
    parameters: schemas.TechnicalIndicatorsHtDcperiodParamsSchema,
    execute: (
      args,
      context // Let type be inferred
    ) =>
      executeAvantageTool(
        "technicalIndicators_htDcperiod",
        args,
        context,
        (av, params) => av.technicalIndicators.htDcperiod(params)
      ),
  });

• src/schemas.ts:234-234 (schema)

  Zod schema for input parameters of the tool, extending common indicator params with series_type.

  export const TechnicalIndicatorsHtDcperiodParamsSchema = TechnicalIndicatorsCommonIndicatorParamsSchema.extend({ series_type: SeriesTypeSchema }).describe('Parameters for HT_DCPERIOD.');

• src/index.ts:1183-1192 (handler)

  Inline handler function for the tool execution, which calls the shared executeAvantageTool with the specific AVantage method for HT_DCPERIOD.

  execute: (
    args,
    context // Let type be inferred
  ) =>
    executeAvantageTool(
      "technicalIndicators_htDcperiod",
      args,
      context,
      (av, params) => av.technicalIndicators.htDcperiod(params)
    ),

• src/index.ts:38-115 (helper)

  Shared helper function used by all tools to manage AVantage client resources, perform API calls via the provided method, handle errors, and return 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}`
      );
    }
  }