MCP Avantage

Instructions

Implementation Reference

• src/index.ts:498-509 (registration)

  Registers the 'crypto_intraday' MCP tool with name, description, input schema, and execute handler using server.addTool.

  server.addTool({
    name: "crypto_intraday",
    description: "Fetches intraday time series data for a cryptocurrency.",
    parameters: schemas.CryptoIntradayParamsSchema,
    execute: (
      args,
      context // Let type be inferred
    ) =>
      executeAvantageTool("crypto_intraday", args, context, (av, params) =>
        av.crypto.intraday(params)
      ),
  });

• src/schemas.ts:104-110 (schema)

  Zod schema defining input parameters: symbol, market, interval, outputsize, datatype for the crypto_intraday tool.

  export const CryptoIntradayParamsSchema = z.object({
    symbol: z.string().describe('The cryptocurrency symbol (e.g., "BTC").'),
    market: z.string().describe('The exchange market (e.g., "USD", "EUR").'),
    interval: MinuteIntervalsSchema,
    outputsize: OutputSizeSchema.default('compact').optional(),
    datatype: DatatypeSchema.default('json').optional(),
  }).describe('Parameters for fetching intraday crypto time series data.')

• src/index.ts:502-508 (handler)

  The execute handler function for the tool, which invokes executeAvantageTool and ultimately calls av.crypto.intraday(params) on the AVantage client.

  execute: (
    args,
    context // Let type be inferred
  ) =>
    executeAvantageTool("crypto_intraday", args, context, (av, params) =>
      av.crypto.intraday(params)
    ),

• src/index.ts:38-115 (helper)

  Generic helper function that manages AVantage client instances, performs the API call via the provided method, handles errors, and returns the result as JSON string. Used by all tools including crypto_intraday.

  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}`
      );
    }
  }