Scrape a public web page and pull caller-specified fields back as clean JSON. Body: {url, fields:[...], instructions?}. 'fields' is a list of field names to extract (e.g. ["price","availability","sku"]); any field not found comes back null. Optional 'instructions' refines how to read the page. Returns {url, fields:{...}}. Common uses: product price/stock monitoring, lead enrichment from company pages, scraping job/listing details. Built on the /scrape extractor plus an LLM extraction pass.