MCP Avantage

Instructions

Implementation Reference

• src/index.ts:1532-1546 (handler)

  The handler implementation for the 'technicalIndicators_atr' tool. It uses a generic executor that calls the Alpha Vantage library's technicalIndicators.atr method with validated parameters.
  server.addTool({ name: "technicalIndicators_atr", description: "Average True Range (ATR)", parameters: schemas.TechnicalIndicatorsAtrParamsSchema, execute: ( args, context // Let type be inferred ) => executeAvantageTool( "technicalIndicators_atr", args, context, (av, params) => av.technicalIndicators.atr(params) ), });
• src/schemas.ts:253-253 (schema)

  Zod schema for input parameters of the technicalIndicators_atr tool, extending the common time period schema with symbol, interval, time_period, and optional datatype/month.
  export const TechnicalIndicatorsAtrParamsSchema = TechnicalIndicatorsTimePeriodOnlyParamsSchema.describe('Parameters for ATR.');
• src/index.ts:1532-1546 (registration)

  Registration of the 'technicalIndicators_atr' MCP tool on the FastMCP server instance.
  server.addTool({ name: "technicalIndicators_atr", description: "Average True Range (ATR)", parameters: schemas.TechnicalIndicatorsAtrParamsSchema, execute: ( args, context // Let type be inferred ) => executeAvantageTool( "technicalIndicators_atr", args, context, (av, params) => av.technicalIndicators.atr(params) ), });
• src/index.ts:26-115 (helper)

  Shared helper function that implements the core logic for all technical indicator tools, including API authentication, resource management, library invocation, and response formatting.
  /** * A generic function to execute an Avantage library method within an MCP tool. * Handles API key resolution, AVantage instance management via ResourceManager, * calling the library method, and handling the response/errors. * * @param toolName The name of the MCP tool (for logging). * @param args Validated tool arguments. * @param context MCP execution context containing extraArgs and requestId. * @param avantageMethod A function that takes the AVantage instance and args, and calls the appropriate library method. * @returns The stringified data from the Avantage library call. * @throws {UserError} If authentication fails or the library call returns an error. */ 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}` ); } }