Source Claim Verification

Check whether a source actually supports a claim.

Paste one claim and one source. You get a verdict — supported, contradicted, partially supported, and more — with the exact passages from the source that decide it.

Options

Payment uses an x402 USDC authorization signed in your browser wallet (e.g. MetaMask). No account needed. We never ask for a private key or recovery phrase.

What you get back

Supported by this source

The source provides sufficient evidence for the material meaning of the claim.

Contradicted by this source

The source materially conflicts with the claim.

Partially supported

The source supports only part of the claim, or supports it only with material limitations (missing qualifier, attribution, narrower scope).

Ambiguous

The source contains potentially relevant material, but the relationship to the claim is not sufficiently clear.

Not found in this source

The source was retrieved and examined, but material supporting or contradicting the claim was not found. This is NOT evidence that the claim is false.

Source unavailable

The source could not be retrieved or reliably parsed. No charge is made for this outcome.

Unable to verify

Evidence was examined but no defensible determination could be made.

This service checks the relationship between a claim and the source you name. It does not decide whether a claim is true everywhere, and it is not legal, medical or financial advice. “Not found in this source” never means “false”.

How it works

  1. The page is fetched once from its public address (no logins, paywalls or CAPTCHAs are bypassed) and cleaned to its readable text.
  2. The passages most relevant to your claim are selected; the claim is split into its parts — who, what, how much, when, where, qualifiers, negation, attribution.
  3. A language model compares the parts with the passages. Every quoted passage is then checked word-for-word against the source, and numbers, dates, negation and “someone claimed” attribution are re-checked by fixed rules.
  4. Claims and sources can be in different languages. Evidence is always shown in the original language; translations are marked as derived.

For AI agents

One call: POST /api/v1/verify with { claim, source_url }. Pay per request with x402 (USDC on Base), 0.048 USDC per verification. Unavailable sources are not charged. See the API docs, OpenAPI and llms.txt.

curl -i https://sourceclaimverification.online/api/v1/verify \
  -H 'content-type: application/json' \
  -H 'idempotency-key: <random 16-128 chars>' \
  -d '{"claim":"The company reported revenue of $3.2 billion in 2025.",
       "source_url":"https://example.com/report"}'
# → 402 with the x402 payment requirement; sign it and repeat with PAYMENT-SIGNATURE