WebFetch gives no guidance that LinkedIn returns HTTP 999 and blocks all fetches

Every LinkedIn URL fetched this session returned HTTP 999 Unknown Status, LinkedIn's own anti-bot response code, not a real server error. The tool description mentions authenticated/private URLs generally, but LinkedIn is probably one of the most commonly attempted fetch targets, and 999 isn't an intuitive status to recognize as "LinkedIn is blocking this" rather than an actual failure.

What should happen: a line in the tool description naming LinkedIn as a known-blocked domain, same as the existing guidance for authenticated services like Google Docs.