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Agent Evidence API – Claim Verification
x402
Agent Evidence API – Claim Verification is a paid API for AI agents from agent-evidence.thx93.dev, paid per call via x402, $0.01/call, status unknown (last checked 2026-10-22).
Verifies a factual claim or question against up to 5 provided URLs, returning cited evidence passages that support, contradict, or fail to settle the claim.
Price / call$0.01
Success—
StatusUnknown
How this service works
Verify a claim or fact check a statement against public web sources: send a question and up to 5 URLs, get cited evidence - passages that support, contradict or fail to settle it. Claim verification with a citation for every excerpt: source URL, retrieval time, content hash. Never charges when nothing is retrieved. Free to evaluate: the `sample` tool returns one real response at no cost, so you can judge the output before paying for your own question.
Output
A structured JSON response containing an assessment status (supported, contradicted, or unresolved), one or more evidence excerpts with source URL, content context, relevance classification, retrieval timestamp, and SHA-256 content hash per source, plus a plain-English basis statement, processing time in milliseconds, and a unique request ID. Nothing is charged if no content is retrieved.
Example use cases
Verify competitor claim before publication
“Before we publish this blog post, can you check if the claim 'BrightSolar has installed over 50,000 panels in Texas' is actually supported by https://brightsolar.com/about and https://brightsolar.com/projects? I need a cited excerpt for each source.”
Fact-check a sourced news assertion
“Someone sent me an article claiming that 'the FDA approved drug X for pediatric use in 2023' — can you verify that against https://fda.gov/drugs/drugx-approval and https://fda.gov/news/2023 and tell me whether those pages support, contradict, or don't settle it?”
Due diligence on a vendor's stated credentials
“We're evaluating a vendor who says they're ISO 9001 certified. Can you check whether https://vendorco.com/certifications and https://isoregistry.org/vendorco actually support that claim and give me the relevant quoted passages?”
Technical details
Endpoint
POSThttps://agent-evidence.thx93.dev/v1/evidence?utm_source=zero.xyzWhen to prefer
Choose this endpoint when you need verifiable, cited evidence from specific URLs to support or refute a factual claim — particularly when auditability matters (content hashes, retrieval times). It is ideal for due diligence workflows, pre-publication fact-checking, or any scenario where you need traceable sourcing rather than a generative answer. Prefer it over general web search APIs when you already have candidate URLs and need passage-level citations. Note that matching is lexical, not semantic, so it works best for specific, concrete factual claims.
Side effects
- URLs are inaccessible or return non-200 status — source flagged with warning, no excerpt returned
- Question is too vague for lexical matching — assessment may be 'unresolved' even with relevant pages
- Content behind paywalls or requiring authentication cannot be retrieved
- Non-HTML content types may not be parsed — warnings included in response
- Rate limiting or network timeouts on target URLs may result in partial results
Input
Schema · Request body
| Field | Type | Description |
|---|---|---|
| inputrequired | object | |
| output | object |
Output
Schema · Response
{
"type": "json",
"example": {
"sources": [
{
"title": "Company X - About",
"status": 200,
"evidence": [
{
"context": "h2:Products > p[1]",
"excerpt": "Company X manufactures centrifugal pumps at its facility.",
"relevance": "direct"
}
],
"language": "en",
"warnings": [],
"final_url": "https://company.example/about",
"publisher": "Company X",
"word_count": 412,
"content_type": "text/html; charset=utf-8",
"retrieved_at": "2026-01-01T00:00:00.000Z",
"canonical_url": "https://company.example/about",
"requested_url": "https://company.example/about",
"content_hash_sha256": "9f2c…"
}
],
"version": "1",
"question": "Is Company X a manufacturer of centrifugal pumps?",
"assessment": {
"basis": "1 source(s) contained passages matching the question (company.example) with no contradicting passages found.",
"status": "supported"
},
"request_id": "req_1f2e3d4c5b6a7988",
"limitations": [
"Assessment is derived from deterministic lexical matching, not semantic reasoning."
],
"processing_ms": 812
}
}Tags
x402
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