get_pit_universe

Use this tool to answer questions about historical index membership — e.g. "Was Company X in the S&P 500 on date Y?" or "Which companies were in the Russell 2000 on 2010-01-01?" Use this INSTEAD OF search_companies when the question involves a specific historical date or whether a company was an index member in the past — search_companies only returns current membership and cannot answer historical questions.

Returns a survivorship-free universe valid on a given as_of_date (only companies that existed and were members on that exact date — no hindsight; [) interval semantics). To check one company, pass its ticker or CIK + the target date: present = was a member, absent = was not.

⚠️ HISTORICAL DEPTH AND PROVENANCE DIFFER BY INDEX — read this before using a result for a backtest.
• **SP500 — back to 1996-01-02, high confidence.** Curated entry/exit spells over 968 CIKs including long-delisted registrants, dated to the actual effective day.
• **RUSSELL1000 / RUSSELL2000 / RUSSELL3000 — back to 2000-09-30, medium confidence.** Reconstructed from publicly disclosed portfolio holdings of large funds that track each index, not from the index provider's own constituent list (which is licensed). Three consequences you must carry into any conclusion: OBSERVATION SPACING VARIES — roughly one to four observations a year from 2000 through 2006, monthly from 2007 on — so a join or leave date is only as precise as the interval between observations and is never exact to the day in the early years; a tracking fund only PROXIES its index, so a few holdings sit outside the index and a sampled fund can miss some members; and there is NO data before 2000-09-30 — an earlier as_of_date returns zero rows because we do not carry it, which is not a statement that the index was empty.
• **Known gap: 2016-12-30 → 2017-07-31.** No holdings observation exists anywhere in that 213-day window, so Russell membership cannot be observed inside it. Departures collapse onto 2016-12-31 and arrivals onto 2017-07-31, which means the June 2017 reconstitution appears to happen on 31 July. Treat Russell results dated inside that window as interpolated.

Returns per company: CIK, ticker, name, sector, industry, SIC code, enriched, and per-row confidence (high/medium/low). The CIK is always present and is the identifier to carry forward; every other identity field is nullable. enriched: false means index_membership names this member but the company has no row in references (it delisted before SEC's current-only ticker map was written) — its identity is UNKNOWN, not absent, and it is still a member. ticker is separately null when the company was not listed under any ticker on the as_of_date.

⚠️ A RESPONSE IS USUALLY A PAGE, NOT THE UNIVERSE. universe_size always reports the FULL matched membership count; returned_rows reports what THIS response carries; complete is true only when they are equal, and survivorship_free is true only when complete is — a slice of a universe is not a survivorship-free universe. Two things shorten a response and they need different fixes: limit defaults to 100 (smaller than every index here), so raise it toward the index size — limit_truncated says when that is what bit; and at most 250 rows are inlined per call whatever your limit, so page with offset using the truncation envelope's next_offset until returned_rows sums to universe_size. To get the whole universe in one read, use get_compute_ready_stream, the Python SDK, or the Bulk Data API. Index rows are ordered by CIK — deliberately uncorrelated with whether a company survived to today, so a truncated page is an arbitrary sample rather than a list of survivors. _meta.pit_safe is true only when EVERY matched row is high-confidence — so it is false for any Russell query by construction. That flag is the one to branch on: use SP500 for rigorous point-in-time work, and treat Russell history as approximate. sector is SIC-derived (GICS-aligned, not licensed GICS) — a screening bucket, not an authoritative label.

Use as the first step of a quantitative backtest before get_compute_ready_stream. Returns an empty array (with error detail) if the date is out of range or has no coverage. Available on every plan — sample returns the subset covered by the sample bucket.