Search the web using DuckDuckGo. Free, no API key required. Use when the user asks to search the web, look something up, find information online, research a topic, or when you need to find current information that isn't in your training data. Also use when web_search tool is unavailable or has no API key configured.

使用 DuckDuckGo 搜索网页，免费且无需 API 密钥。当用户要求搜索网页、查找信息、在线研究主题，或你需要获取训练数据中没有的最新信息时使用。当 web_search 工具不可用或未配置 API 密钥时，也请使用此功能。