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Agent Evidence API – Claim Verification with Cited Web Sources
x402
Agent Evidence API – Claim Verification with Cited Web Sources is a paid API for AI agents from agent-evidence-api.thx93.workers.dev, paid per call via x402, $0.03/call, status down (last checked 2026-10-14).
Verifies a claim against up to 5 provided URLs, returning excerpts from those pages that support, contradict, or fail to settle the claim, each with a source URL, retrieval timestamp, and content hash.
Price / call$0.03
Success—
StatusDown
How this service works
Verify a claim 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.
Output
The agent receives a structured response containing excerpts (passages) from the retrieved web pages, each labeled as supporting, contradicting, or inconclusive with respect to the claim. Every passage includes its source URL, the time it was retrieved, and a content hash for integrity verification. If no content is retrieved from any URL, no charge is incurred and an appropriate empty or error response is returned.
Example use cases
Fact-checking a political statement
“I saw a politician claim that 'US renewable energy now accounts for 25% of electricity generation' — can you check that against https://www.eia.gov/energyexplained/renewable-sources/ and https://www.iea.org/reports/renewables-2023 and show me the passages that support or contradict it with citations?”
Verifying a health product claim
“A supplement brand says their product 'clinically proven to reduce cholesterol by 15%' — please verify that claim against https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1234567/ and https://www.mayoclinic.org/diseases-conditions/high-blood-cholesterol/symptoms-causes/syc-20350800 and tell me what the evidence actually says.”
Checking a company's ESG claims
“Our compliance team needs to verify whether Acme Corp's claim that they achieved 'net zero emissions in 2023' is supported by their own sustainability report at https://www.acmecorp.com/sustainability-report-2023 and the third-party audit at https://www.cdp.net/en/companies/acme — pull out the relevant passages and flag anything that contradicts the claim.”
Technical details
Endpoint
POSThttps://agent-evidence-api.thx93.workers.dev/mcp?utm_source=zero.xyzWhen to prefer
Choose this endpoint when an agent needs to verify a specific factual claim against authoritative or user-supplied URLs with full citation provenance (source URL, retrieval time, content hash). It is ideal for fact-checking workflows, compliance checks, research validation, or any scenario where the agent must justify its verdict with traceable evidence rather than relying on its own training knowledge. Prefer it over a general web search API when you already have candidate source URLs and need passage-level citation rather than a ranked list of links.
Side effects
- URL is inaccessible, paywalled, or returns a non-200 response — no content retrieved for that source
- Claim is too ambiguous for passages to be classified as supporting or contradicting — returned as inconclusive
- All provided URLs fail to return content — no charge incurred but no evidence returned
- Rate limiting or network timeouts on external URL fetches — partial results or empty response
- Malformed input schema or missing required fields — request rejected with validation error
- URL content has no textual overlap with the claim — all passages returned as inconclusive
Input
Schema · Request body
| Field | Type | Description |
|---|---|---|
| inputrequired | object | |
| output | object |
Tags
x402
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