Call this with a ``doc_id`` returned by ``search_docs`` (or a slug such as
``ymZimX7JLe``). Manuals are often 20k-60k characters, so this tool
paginates: if the reply has ``truncated: true`` and a ``next_offset``,
call again with that ``offset`` to continue. Do not re-request the same
offset.
Args:
doc_id: id from search_docs (also accepts the page slug).
max_chars: characters per call, default 20000, max 120000.
offset: start position, default 0.
Returns JSON: {doc_id,title,space,url,chars,offset,returned,truncated,
next_offset,updated_at,content}. Always cite ``url``.