SML ClaimGate — claim fact-checks with quote-verified evidence for AI agents

What does it cost to fact-check a claim with an AI agent? ClaimGate pricing

ClaimGate fact-checks any claim against live web sources for 0.25 USDC. Your agent sends a claim; ClaimGate decomposes it into sub-claims, fetches the sources live, and has Jev jurors judge each independent source family — every judgment backed by an exact quote that ClaimGate machine-verifies against the fetched text before it counts. A coherence gate then issues the verdict — SUPPORTED, CONTRADICTED, MIXED, or an honest UNVERIFIABLE — and seals the whole evidence pack as a receipt your agent can re-fetch forever, free. Payment is USDC on Base via x402 (the open protocol built on HTTP's 402 "Payment Required" status, so machines can pay per call in stablecoins). No subscription, no account, no API key.

Pricing at a glance

Start free: call fact_check_preview on POST https://scriptmasterlabs.com/claimgate/mcp with any claim — the fetch plan costs nothing. The 402 challenge on the paid tool is the documentation.

Claim in → sources fetched → verbatim-quote evidence → coherence-gated verdict → sealed receipt out.

The proving settlements

Launch-day proof checks, run 2026-10-30 from the owner's proof wallet (SELF-PROOF — real on-chain settlements, not customer purchases; published, dated, and independently checkable, with receipt ids anyone can re-fetch free via fact_check_receipt or GET https://claimgate.onrender.com/receipts/<id>):

Receipt persistence was proven the same day: the SUPPORTED receipt was re-fetched byte-identical after a full service redeploy — receipts live in SQLite on a persistent disk, not in process memory. A 402 challenge is not a settlement; a transaction hash with status success, plus a receipt you can re-fetch, is.

How the verdict is computed (the methodology is the product)

ClaimGate uses ScriptMasterLabs' coherence formula — the same measurable that gates trades in PRO-LO and payments on Arc. Per independent source family (syndicated copies of one story are one family; pages on one domain are one family), a Jev juror (jev-1.13.0) returns a direction d: +1 supports, −1 contradicts, 0 does-not-address — and must cite evidence as an exact quote from that family's fetched text. The server whitespace-normalizes and verifies the quote literally exists in the fetched text; a quote that fails verification is discarded and counted in the receipt, and a family whose quotes all fail casts no vote. Families are weighted by source class: primary/official = 3, reputable secondary = 2, other = 1. coherence = |Σ w·d| / Σ w over addressing families.

Honest limits: ClaimGate's verdicts are labeled calibrated: false — the thresholds are stated and fixed, but the jury has not been benchmarked against a labeled fact-check corpus, and this page does not pretend otherwise. Blocked, paywalled or failed sources are recorded in the receipt as failed fetches and are never treated as evidence. ClaimGate checks claims against web sources; it does not certify ground truth, and an UNVERIFIABLE verdict means the public web did not settle the question — not that the claim is false.

Fact check vs preview vs no check

How a call works

1. POST a claim to https://scriptmasterlabs.com/claimgate/mcp (tool fact_check_claim) or https://claimgate.onrender.com/fact-check. The service answers 402 with an x402 challenge (USDC, Base mainnet eip155:8453, payTo (the receiving wallet the payment settles to) 0xc29185fa176357612f3194735753e520e91adc46), including the bazaar discovery extension.
2. Sign the EIP-3009 authorization (the Ethereum standard that lets a signed approval move tokens on the payer's behalf — the mechanism x402 settlements use) and resend with the PAYMENT-SIGNATURE header.
3. The payment is verified, sources are fetched, jurors judge with quote evidence, the coherence gate decides, and the receipt is sealed and persisted — then settlement fires and the response carries the verdict, the coherence score, and the settlement transaction.
4. Re-fetch the full evidence pack any time, free: tool fact_check_receipt or GET https://claimgate.onrender.com/receipts/<receipt_id>.

{
  "claim": "Your claim, stated as one checkable sentence.",
  "sources": ["https://example.com/optional-source"]
}

Machine buyers start here: the x402 discovery document at https://claimgate.onrender.com/.well-known/x402 lists the tolled routes and terms; the methodology tool returns the complete scoring rules in machine-readable form.

Frequently Asked Questions

Q: How much does ClaimGate cost?

A: One fact check costs 0.25 USDC (fact_check_claim over MCP, or POST /fact-check over plain HTTP). Payments are USDC on Base mainnet (eip155:8453) via x402, settled to 0xc29185fa176357612f3194735753e520e91adc46. The preview, status, methodology and receipt tools are free. There is no subscription, no account and no API key.

Q: What does a ClaimGate fact check return?

A: A sealed receipt: the claim and its hash, the sub-claims it was decomposed into, every fetched source with its fetch status and content hash, a per-source-family verdict backed by a verbatim quote that was machine-verified against the fetched source text, the coherence score, the verdict (SUPPORTED, CONTRADICTED, MIXED or UNVERIFIABLE), and the settlement transaction. The receipt is retrievable any time, free, by receipt id.

Q: How does ClaimGate decide a verdict?

A: Per independent source family (syndicated copies and same-domain pages count as one family), a Jev juror returns a direction — supports (+1), contradicts (−1) or does-not-address (0) — and must cite an exact quote from the fetched source; the server verifies the quote literally exists in the fetched text and discards votes whose quotes fail. Families are weighted by source class (primary/official 3, reputable secondary 2, other 1). Coherence = |Σ w·d| / Σ w over addressing families. SUPPORTED requires coherence ≥ 0.80, a positive net direction, and at least 2 independent addressing families; CONTRADICTED mirrors it; 0.50–0.79 is MIXED; anything else is UNVERIFIABLE. ClaimGate never guesses.

Q: Is ClaimGate live?

A: Yes. On 2026-10-30 three launch-day proof checks settled real USDC on Base mainnet: a true claim returned SUPPORTED at coherence 0.857 (settlement transaction 0x6e5b9306406c03a5bf13e7d7409b2335ee1c1e3f4e2d82192b051a0d5cfc03ab, Base block 53,288,011); a false claim and an unverifiable claim both returned UNVERIFIABLE and never SUPPORTED. These were owner proof-wallet self-tests (SELF-PROOF), published with their receipt ids so anyone can re-fetch the full evidence packs.

Q: Is there a pay-per-use option?

A: Yes. ClaimGate is pay-per-use only: 0.25 USDC per fact check, paid per call in USDC on Base (eip155:8453) via x402. Previewing what would be checked, reading the status and methodology, and fetching receipts are free. An unpaid request receives the 402 challenge only; nothing settles.

Start

Start free — preview any claim: call fact_check_preview at POST https://scriptmasterlabs.com/claimgate/mcp. When you need the verdict, the same endpoint's fact_check_claim settles at 0.25 USDC per check.

Related verification tools from ScriptMasterLabs: Verdict Protocol — signed decision receipts for agents that manage real capital; Decision-Gated Machine Payments — the pattern behind the coherence gate; Which payment networks support the x402 protocol? — the full network map.