MCP Avantage

Instructions

Implementation Reference

• src/index.ts:1028-1042 (registration)

  Registers the 'technicalIndicators_dema' MCP tool with name, description, input schema, and inline execute handler that delegates to executeAvantageTool and the AVantage library's dema method.

  server.addTool({
    name: "technicalIndicators_dema",
    description: "Double Exponential Moving Average (DEMA)",
    parameters: schemas.TechnicalIndicatorsTimeSeriesIndicatorParamsSchema,
    execute: (
      args,
      context // Let type be inferred
    ) =>
      executeAvantageTool(
        "technicalIndicators_dema",
        args,
        context,
        (av, params) => av.technicalIndicators.dema(params)
      ),
  });

• src/index.ts:1032-1041 (handler)

  The execute handler function for the tool, which calls the generic executeAvantageTool helper passing the AVantage library's technicalIndicators.dema method.

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

• src/schemas.ts:212-215 (schema)

  Defines the Zod input parameters schema for the tool: symbol, interval, optional datatype/month, plus time_period and series_type.

  export const TechnicalIndicatorsTimeSeriesIndicatorParamsSchema = TechnicalIndicatorsCommonIndicatorParamsSchema.extend({
    time_period: z.string().describe('Number of data points used to calculate the indicator.'), // Using string as AV API expects string
    series_type: SeriesTypeSchema,
  }).describe('Parameters for time series based technical indicators.')

• src/index.ts:38-115 (helper)

  Generic helper function used by all tools (including this one) to resolve API key, manage AVantage client instance via resource manager, invoke the specified library method, handle errors, and return JSON string of 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:204-209 (schema)

  Base schema extended by the tool's parameters schema, defining common fields: symbol, interval, datatype, month.

  export const TechnicalIndicatorsCommonIndicatorParamsSchema = z.object({
    symbol: z.string().describe('The stock symbol (e.g., "IBM").'),
    interval: z.string().describe('Time interval (e.g., "daily", "60min", "weekly"). Check Alpha Vantage docs for valid intervals per indicator.'),
    datatype: DatatypeSchema.default('json').optional(),
    month: z.string().optional().describe('Specific month for intraday intervals (YYYY-MM format).'),
  }).describe('Common parameters for many technical indicators.')