Function: add_to_watchlist
Description: This tool belongs to the trading system, which allows users to trade stocks, manage their account, and view stock information. Tool description: Add a stock to the watchlist.
Parameters:
type: dict
properties: stock: type: string
description: the stock symbol to add to the watchlist. 
required: stock
Response:
type: dict
properties: symbol: type: string
description: the symbol that were successfully added to the watchlist.