Lenz Fact-Check
Fact-check factual claims against independent sources.
Community: Submitted by a user or imported; check the owner before granting accessOnlineNo sign-inGlobalFreeRead-only
What it can do
- Assess Claim: Fast fact-check: a verdict in ~5-10s via a 3-model panel. Use this as the default for checking a factual claim. Returns one verdict per atomic claim found in ``claim`` (True / Mostly Tru
- Verify Claim: Start a deep, multi-step fact-check (research → debate → adjudication). Reserve for high-stakes claims that warrant a thorough, sourced investigation — it takes ~90s and uses scarce deep
- Select Claims: Resolve a `needs_input` verification by choosing which claim(s) to run. When `get_verification` returns ``status: needs_input`` with reason ``multi_claim`` or ``clarification_required``
What data it sees
Do you need an account
No: the server works without sign-in
Fact-check factual claims against independent sources. assess gives a fast multi-model verdict (True → False) with bucketed confidence in ~5–10s; verify runs a deeper research → debate → panel investigation for high-stakes claims and returns sourced, pollable results. ask answers grounded follow-ups on a completed verification. Verdicts are directional, not absolute. Connect via OAuth or a free Lenz API key.
Server tool list (6)
Raw names from tools/list. Only developers need these.
| assess_claim | Fast fact-check: a verdict in ~5-10s via a 3-model panel. Use this as the default for checking a factual claim. Returns one verdict per atomic claim found in ``claim`` (True / Mostly True / Mixed / Mostly False / False) plus a bucketed confidence. Cheaper and faster than `verify_claim`; no detailed sources. If the text is ambiguous it returns candidate readings to re-assess; if it contains no checkable claim it says so. ``language`` is an optional ISO code for the response language. |
| verify_claim | Start a deep, multi-step fact-check (research → debate → adjudication). Reserve for high-stakes claims that warrant a thorough, sourced investigation — it takes ~90s and uses scarce deep-check quota. Returns a ``task_id`` immediately; call `get_verification(task_id)` until its status is ``completed`` to retrieve the sourced result. For a quick answer use `assess_claim` instead. |
| select_claims | Resolve a `needs_input` verification by choosing which claim(s) to run. When `get_verification` returns ``status: needs_input`` with reason ``multi_claim`` or ``clarification_required``, call this with that ``task_id`` and a ``claims`` list containing one or more of the offered claim texts (from the `claims`/`candidates` it returned). Each selected claim starts its own deep verification; poll each returned ``task_id`` with `get_verification`. (Not for ``duplicate_found`` — use the surfaced `similar_claims` there instead.) |
| get_verification | Retrieve (or poll) a deep `verify_claim` result by its ``task_id``. While running, returns ``status: processing``. If the claim needs a decision (multiple claims, ambiguity, or a near-duplicate), returns ``status: needs_input`` with the options. When finished, returns ``status: completed`` with the verdict, confidence, executive summary, top sources, and the ``verification_id`` — pass that to `ask_followup` for a grounded follow-up. (No Lenz link: deep-check claims are private to the caller, so a claim-page link would be share-gated rather than publicly viewable.) |
| check_usage | Return remaining Lenz quota for the calling key, per capability. Reports remaining ``assess`` and ``verify`` capacity (and the current plan). Call this before a batch of checks to avoid hitting a quota wall mid-run. |
| ask_followup | Ask a grounded follow-up question about a completed `verify_claim` result. The `verify_claim`/`get_verification` result is trimmed; this reads the FULL evidence (research, debate, per-panelist adjudication, all sources) the trimmed payload omits and answers ``question`` from it. Pass the ``verification_id`` returned by `get_verification` (NOT a task_id). Only works on a completed `verify_claim` — not on `assess_claim` results. Uses your `ask_followup` quota. The conversation is kept server-side per verification, so ask follow-ups sequentially rather than in parallel. ``language`` is an optional ISO code for the reply language. |