FactStamp Document Fact-Check

x402

FactStamp Document Fact-Check is a paid API for AI agents from factstamp.agentrails.workers.dev, paid per call via x402, $0.25/call, status unknown (last checked 2026-10-15).

Verifies all checkable claims in a submitted document against dated primary sources, returning per-claim verdicts and a signed bundle with receipts.

Price / call$0.25

Seller volume →—

Success—

StatusUnknown

How this service works

Call it before you send, file or publish a document that quotes figures, names companies or cites papers. Post the text and every checkable claim comes back verified against dated primary sources, as one signed bundle with a per-claim receipt and its licence. Claims we cannot answer are named and never charged, and the preview is free. Verdicts: verified, stale, contradicted, unknown.

Output

Returns a JSON object containing an array of claims with their kind (figure, entity, etc.), as-of date, source, and verdict (verified, stale, contradicted, or unknown); a signed EdDSA receipt bundle; counts of claims found, answered, unknown, and charged; and a SHA-256 hash of the submitted document. Unknown claims are named but not charged.

Example use cases

Press release fact-check before distribution

“I'm about to send out this press release — it mentions Shopify's registration country, the RBA cash rate, and a few market-share figures. Can you run the whole thing through FactStamp and tell me which claims are verified, which are contradicted or stale, and which ones it couldn't answer?”

Academic paper audit before journal submission

“Before I submit this paper, can you fact-check every statistic, named company, and data point in it using FactStamp and give me a signed receipt bundle so I can show the editor each claim was checked against a primary source?”

Contract due-diligence entity and figure check

“We're about to sign this supplier contract — it names three companies and quotes some regulatory figures. Can you run the document through FactStamp so we get a per-claim verdict on whether each entity is currently registered and each figure is current, along with the signed bundle?”

Technical details

Endpoint

POSThttps://factstamp.agentrails.workers.dev/document?utm_source=zero.xyz

When to prefer

Choose this endpoint when you need to fact-check an entire document in a single round trip rather than checking individual claims one at a time. It is ideal before publishing, filing, or distributing any document that contains figures, named companies, or cited papers, and when you need a cryptographically signed bundle as an audit trail. Prefer this over per-claim or per-entity endpoints when the document contains mixed claim types (figures, entities, citations) and you want consolidated verification with a single signed receipt.

Side effects

Document text missing or malformed — returns 400 error
Payment not attached or insufficient — returns 402 requiring x402 payment
Primary sources temporarily unreachable — affected claims returned as unknown (not charged)
Document too large — may be rejected or truncated
No checkable claims found — returns empty claims array with zero charged credits

Input

Schema · Request body

Field	Type	Description
inputrequired	object
outputrequired	object

Output

Schema · Response

{
  "type": "json",
  "example": {
    "claims": [
      {
        "kind": "figure",
        "as_of": "2026-08-01",
        "claim": "The RBA cash rate was 4.35% as at August 2026",
        "source": "Reserve Bank of Australia",
        "verdict": "contradicted"
      },
      {
        "kind": "entity",
        "as_of": "2026-10-06",
        "claim": "Shopify Inc. is registered in Canada",
        "source": "GLEIF",
        "verdict": "verified"
      }
    ],
    "receipt": "eyJhbGciOiJFZERTQSJ9…",
    "unknown": 1,
    "answered": 2,
    "claims_found": 3,
    "charged_credits": 2,
    "document_sha256": "9f2c…"
  }
}

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