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Claim Verification
x402
Claim Verification is a paid API for AI agents from x402.agentindex.world, paid per call via x402, $0.001/call, status unknown (last checked 2026-10-03).
Checks whether a given source text supports, contradicts, or gives insufficient information about a factual claim, returning a typed verdict with a probability score.
Price / call$0.001
Success—
StatusUnknown
How this service works
Check whether a source supports, contradicts, or gives insufficient information about a claim - a typed verdict with a real probability, not generated text. Try GET /verify/sample.
Output
A typed verdict indicating whether the source supports, contradicts, or gives insufficient information about the claim, paired with a real probability score (not free-form generated text).
Example use cases
Fact-checking news article claims
“I have a claim that 'Global CO2 emissions fell by 7% in 2020' and a paragraph from an IPCC report — can you tell me whether the report supports, contradicts, or is inconclusive about that claim, and how confident you are?”
Research citation validation
“I wrote in my paper that 'mRNA vaccines do not alter human DNA' — can you check whether this abstract I have from a Nature journal article actually supports that claim, and give me a probability?”
Legal document consistency check
“Our contract clause says 'delivery is guaranteed within 5 business days' — does this email thread from the supplier support or contradict that claim? I need a verdict and confidence score.”
Technical details
Endpoint
GEThttps://x402.agentindex.world/verify?utm_source=zero.xyzWhen to prefer
Choose this endpoint when you need a structured, probabilistic verdict on whether a specific text passage supports or refutes a claim — not free-form summarization. It is ideal for fact-checking pipelines, RAG validation, citation auditing, or any workflow requiring a machine-readable true/false/inconclusive classification with a confidence score rather than a generated explanation.
Side effects
- Missing 'claim' or 'source' field returns a 400 validation error
- Source text too short or uninformative may result in 'insufficient information' verdict with low confidence
- Payment failure or missing x402 header returns a 402 Payment Required response
- Very long source texts may be truncated or cause timeouts
- Ambiguous or compound claims may yield uncertain probabilities near 0.5
Input
Schema · Request body
| Field | Type | Description |
|---|---|---|
| claim | string | The factual claim to check. |
| source | string | The source text to check the claim against. |
Output
Schema · Response
{
"type": "json",
"example": {
"verdict": "supported",
"confidence": 1,
"probability": 1,
"x402_receipt": {
"upstream": "verification",
"latency_ms": 390,
"model_served": "jev",
"price_paid_usdc": 0
},
"probabilities": {
"supported": 1,
"contradicted": 0,
"not_enough_info": 0
}
}
}Tags
x402
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