Quickstart

pip install lenz-io

npm install lenz-io

pipx install "lenz-io[cli]"

from lenz_io import Lenz

client = Lenz()  # reads LENZ_API_KEY
rows = client.assess(
    claim="The Great Wall of China is visible from space.",
).claims
for c in rows:
    print(c.verdict, c.confidence)  # e.g. False high
    if c.rationale:
        print(c.rationale)

import { Lenz } from "lenz-io";

const client = new Lenz(); // reads LENZ_API_KEY
const { claims } = await client.assess({
  claim: "The Great Wall of China is visible from space.",
});
for (const c of claims) {
  console.log(c.verdict, c.confidence); // e.g. False high
  if (c.rationale) console.log(c.rationale);
}

lenz assess "The Great Wall of China is visible from space."

curl -X POST https://lenz.io/api/v1/assess \
  -H "Authorization: Bearer $LENZ_API_KEY" \
  -H "X-Lenz-API-Version: 2026-10-11" \
  -H "Content-Type: application/json" \
  -d '{"claim": "The Great Wall of China is '\
'visible from space."}'

v = client.verify_and_wait(
    claim="The Great Wall of China is visible from space.",
)
print(v.verdict, v.lenz_score)  # e.g. False 2
print(v.key_finding)
for s in v.sources[:2]:
    print(s.title, s.url)

const v = await client.verifyAndWait({
  claim: "The Great Wall of China is visible from space.",
});
console.log(v.verdict, v.lenz_score); // e.g. False 2
console.log(v.key_finding);
for (const s of (v.sources ?? []).slice(0, 2)) {
  console.log(s.title, s.url);
}

lenz verify "The Great Wall of China is visible from space."

draft = (
    "The EU AI Act entered into force on 1 August 2024. "
    "Fines for prohibited practices reach 7% of "
    "global annual turnover. About 40% of European "
    "companies had started compliance work by the "
    "end of 2024."
)
review = client.review_and_wait(text=draft)
# clean | issues_found | incomplete | unchecked
print(review.outcome)
for i in review.issues:
    print(i.verdict, i.claim)
    if i.suggested_rewrite:
        print("  Suggested rewrite:", i.suggested_rewrite)

const draft =
  "The EU AI Act entered into force on 1 August 2024. " +
  "Fines for prohibited practices reach 7% of " +
  "global annual turnover. About 40% of European " +
  "companies had started compliance work by the " +
  "end of 2024.";
const review = await client.reviewAndWait({ text: draft });
// clean | issues_found | incomplete | unchecked
console.log(review.outcome);
for (const i of review.issues) {
  console.log(i.verdict, i.claim);
  if (i.suggested_rewrite) {
    console.log("  Suggested rewrite:", i.suggested_rewrite);
  }
}

# quick verdicts first, each row rewritten as its deep check lands
lenz review draft.md

check = client.citecheck_and_wait(pairs=[{
    "statement": "Mount Everest is 7,000 metres high.",
    "url": "https://en.wikipedia.org/wiki/Mount_Everest",
}])
for c in check.citations:
    # result is None when the check failed on our side
    finding = c.result.finding if c.result else "failed"
    print(finding, c.check.snippet)

const check = await client.citecheckAndWait({
  pairs: [{
    statement: "Mount Everest is 7,000 metres high.",
    url: "https://en.wikipedia.org/wiki/Mount_Everest",
  }],
});
for (const c of check.citations) {
  // result is null when the check failed on our side
  console.log(c.result?.finding ?? "failed", c.check.snippet);
}

# pairs from stdin (or --pairs pairs.json); a draft file works too: lenz citecheck draft.md
echo '[{"statement": "Mount Everest is 7,000 metres high.",
  "url": "https://en.wikipedia.org/wiki/Mount_Everest"}]' \
  | lenz citecheck --pairs -

reply = client.ask.send(
    v.verification_id,
    message="Which source is strongest?",
)
print(reply.content)

const reply = await client.ask.send(v.verification_id, {
  message: "Which source is strongest?",
});
console.log(reply.content);

lenz ask <verification_id> "Which source is strongest?"