Returns matching sections with excerpts, headings, scores, and hierarchy.

current_only=True (default) returns only text in effect now. eCFR's own
"current" index still lists some superseded and removed versions, so
each hit is checked against the section's version history: older
copies of a section are dropped, and hits whose text has since been
replaced or removed are dropped and listed under current_check
('superseded' with the current version's date, 'removed' with the
removal date). Up to 10 parts per page are checked; any hit not
checked is marked. current_only=False returns every historical
version, so a section amended 5 times appears 5 times.

Search caps at 10,000 total results. Use hierarchy filters (title,
chapter, part) to narrow if you hit the cap. chapter/part/subpart/section
filters need a title; without one, title 48 is assumed (title_assumed
says so). Labels like 'FAR Part 15', 'Subpart 15.3' or '§ 52.212-5' are
read as 15, 15.3 and 52.212-5. Most titles other than 48 number chapters
in Roman numerals (2 CFR chapter 'II').

order controls result ordering: 'relevance' (default), 'newest_first',
'oldest_first', 'hierarchy', or 'citations'.

agency_slugs filters to one or more agencies (single slug string or a
list, e.g. 'defense-acquisition-regulations-system'). Use list_agencies()
to find slugs.

last_modified_after/before use YYYY-MM-DD format and filter by the
date sections were last amended. Useful for finding recent regulatory changes.

per_page accepts 1 to 5000 (default 20); paginate with page for more.