WebFetchIncisive

Fetch and extract unsummarized content from URLs as markdown.

Unlike web_fetch, fetches through the user's device instead of proxying through Anthropic's servers. Uses precise content extraction techniques and clean first-party APIs for navigating content instead of summarization. Use this for a rich content exploring experience that is not subject to 403 bans of data-center subnets, or when web_fetch is rejected with PERMISSIONS_ERROR.

Targeted extraction (preferred over fetching full pages):

• section="Syntax" — extract a specific section by heading name

• auto_expand=True — with section=, also return everything filed under that heading (its subsections). Off by default: a heading's subtree can be one to two orders of magnitude larger than its own content, so ask for it when you want a whole chapter, a clause with its sub-clauses, or a comment with its replies in one call

• search="terms" — keyword search over ~500-token slices, ranked by BM25

• slices=[3, 4, 5] — retrieve specific slices by index

• URL fragments (#section-name) are resolved automatically as sections

RECOMMENDED WORKFLOW: For pages of substantial or unknown length, call web_fetch_sections first to map the heading tree, then come back here with precise section= or slices= targets. A full-page fetch is rarely the right first move — it fills context with material you don't need and discards the structural information that makes follow-up queries cheap. For Reddit threads, web_fetch_sections returns the comment tree instead.

search= operators (tantivy query language):

• foo bar — match any term (whitespace is OR)

• +foo +bar — require both terms

• foo -bar — exclude 'bar'

• "exact phrase" — adjacent words in order

• "some words"~3 — phrase with up to 3-word gaps

• (foo OR bar) baz — grouping + AND/OR/NOT

• foo~ — fuzzy match (edit distance) Matching is case-insensitive; no stemming (search for both 'prompt' and 'prompts' if you want either). Stray punctuation in natural-language queries is silently dropped. Scripts written without spaces between words (Japanese, Chinese, Korean, Thai) are indexed by character n-gram: write each term unspaced, as it appears in the text, and it will match inside a clause. Such a term matches within one punctuation-delimited clause, so do not join across a 、 or 。

For Wikipedia and other MediaWiki pages, a dedicated companion tool offers footnote and inline-citation resolution that this fast path can't provide. When the target page has those reference types, the response frontmatter surfaces a see_also hint pointing at it.

Always use this tool for Reddit URLs — built-in fetch tools cannot access Reddit content when proxied. Handles posts, subreddit listings, user pages, and comment permalinks; a permalink scopes output to the linked comment while caching the whole thread for follow-up section=/slices= queries.

JavaScript-dependent pages: a plain fetch returns static HTML. When that comes back as an empty shell, the response frontmatter says so — retry with requires_js=true to render through a headless browser. requires_js is the heavier path; reach for it in response to that signal, not by default. Pass actions to run a ReAct interaction chain before extraction (supplying actions implies requires_js):

• {"action": "click", "selector": "button#submit"}

• {"action": "fill", "selector": "input[name=query]", "value": "search term"}

• {"action": "select", "selector": "select#region", "value": "us-east"}

• {"action": "wait", "selector": ".results-loaded"} A browser render annotates interactive elements for follow-up actions; max_elements caps that list, and 0 omits it.

Supports HTML, plain text, JSON, and XML content types.