Triggered when the user asks for page-level interaction with a specific webpage: login, form filling, button clicks, pagination scraping, screenshots, downloading page images, handling CAPTCHAs or anti-bot measures, accessing SPA dynamic content; also used as a fallback when WebFetch returns an empty shell or gets blocked. Typical phrasing: "log me into X then scrape Y", "take a screenshot". **Not for**: factual questions or "what is xx" (→ `WebSearch`), or simply reading static webpage text (try `WebFetch` first).