MCP Avantage

Instructions

Implementation Reference

• src/index.ts:1255-1269 (registration)

  Registers the 'technicalIndicators_natr' MCP tool with the server, including its description, input schema, and execute handler that wraps the Alpha Vantage library call.
  server.addTool({ name: "technicalIndicators_natr", description: "Normalized Average True Range (NATR)", parameters: schemas.TechnicalIndicatorsNatrParamsSchema, execute: ( args, context // Let type be inferred ) => executeAvantageTool( "technicalIndicators_natr", args, context, (av, params) => av.technicalIndicators.natr(params) ), });
• src/index.ts:1259-1268 (handler)

  The execute handler function for the tool, which invokes executeAvantageTool to call the Alpha Vantage natr method with validated parameters.
  execute: ( args, context // Let type be inferred ) => executeAvantageTool( "technicalIndicators_natr", args, context, (av, params) => av.technicalIndicators.natr(params) ),
• src/schemas.ts:243-243 (schema)

  Defines the Zod input validation schema for the tool, aliasing the time_period-only params schema for NATR.
  export const TechnicalIndicatorsNatrParamsSchema = TechnicalIndicatorsTimePeriodOnlyParamsSchema.describe('Parameters for NATR.');
• src/index.ts:38-115 (helper)

  Shared utility function used by all Alpha Vantage tools: manages authentication, client pooling via ResourceManager, executes the specific AVantage method, handles errors, and returns JSON 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}` ); } }