**Tool Name**: `web`
Research public web information and programming documentation. Use search with query or open with url or cached reference. With active openai-codex, search uses the active model and Codex OAuth to return a labeled synthesis with URL citations, not page extracts or cached references. Other providers use Exa search, requiring EXA_API_KEY. URL open fetches public HTTP(S) directly without credentials or an Exa key, returning bounded readable text. No redirects, private networks, JavaScript, or browser interaction. No error fallback between search backends. Cached references last only for this runtime and may be evicted. Unused fields must be omitted or null.
Exa search accepts optional domainFilter (up to 20 bare ASCII domains, 253 characters per domain and 63 per label; prefix '-' to exclude) and recencyFilter (day/week/month/year: publication dates within 1/7/30/365 days from the current UTC date, not crawl freshness). Codex search rejects both filters; omit them. Search limit is a source-count target on Codex, not a guaranteed count. Filters are search-only. Cached open never refreshes. Output supplies no publication/crawl/fetch timestamps, so do not infer freshness.