Web Evidence API – Claim Verification

x402

Web Evidence API – Claim Verification is a paid API for AI agents from api.aisoup.net, paid per call via x402, $0.05/call, status unknown (last checked 2026-10-13).

Verifies a text claim against web sources, returning a verdict, cited evidence, source snapshots, cryptographic hashes, and conflict detection

Price / call$0.05

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Success—

StatusUnknown

How this service works

Machine-discoverable services AI agents can call and purchase autonomously.

Output

Returns a JSON object containing: a verdict status (e.g. confirmed, unconfirmed, contested), a natural-language conclusion, an array of cited evidence items with URLs and excerpts, a list of atomic facts extracted, any conflicting sources, web snapshots with hashes for provenance, a timestamp of when verification was observed, a unique verification ID, provider sources used, and any limitations of the verification.

Example use cases

Journalist verifying a statistical claim

“I need you to verify this claim before I publish: 'Apple became the first company to reach a $3 trillion market cap in January 2022' — use authoritative sources only, find at least 2 sources, and flag any conflicting information you find.”

Legal compliance check on a regulatory fact

“Can you check whether this is accurate: 'GDPR fines can reach up to 4% of a company's global annual turnover' — limit results to official or authoritative sources only, jurisdiction EU, and snapshot the evidence so I have a record.”

AI agent self-verification of generated output

“Before I send this to the user, verify this fact I just generated: 'The Base mainnet chain ID is 8453' — open web sources are fine, get up to 3 sources, and tell me if anything conflicts.”

Technical details

Endpoint

POSThttps://api.aisoup.net/v1/claims/verify?utm_source=zero.xyz

When to prefer

Choose this endpoint when you need cited, verifiable evidence for or against a specific factual claim — especially when you need source snapshots and cryptographic provenance for auditability. Prefer it over general web search when the output must include a structured verdict, conflict detection, and hash-anchored evidence suitable for compliance, journalism, or agent self-verification workflows. Particularly useful when you need jurisdiction-scoped or domain-filtered verification with freshness controls.

Side effects

Claim is too vague or ambiguous for sources to confirm — returns unconfirmed status with explanation
Freshness constraint too tight — no sources found within the requested time window
All candidate domains blocked — returns error if no sources available after filtering
Claim exceeds 4000 character limit — returns 400 validation error
Minimum source threshold not met — returns result noting insufficient sources found
Payment failure via x402/MPP — returns 402 Payment Required
Rate limiting or upstream web access failure — returns 503 or timeout

Input

Schema · Request body

Field	Type	Description
asOf	—	Optional date at which the claim should be evaluated.
claim	string	The factual claim to verify.
language	string	Preferred response language or auto.
maxSources	integer	Maximum number of evidence sources to return.
jurisdiction	—	Optional country, state, or legal jurisdiction.
sourcePolicy	—	Policy controlling which kinds of web sources may be used.
allowedDomains	array	Optional hostname allowlist without schemes or paths.
blockedDomains	array	Optional hostname blocklist without schemes or paths.
freshnessHours	—	Maximum preferred source age in hours.
minimumSources	integer	Minimum number of evidence sources requested.
includeConflicts	boolean	Whether to search for and report conflicting evidence.

Output

Schema · Response

{
  "type": "json",
  "example": {
    "claim": "The Base mainnet chain ID is 8453.",
    "status": "confirmed",
    "evidence": [],
    "conflicts": [],
    "snapshots": [],
    "conclusion": "Authoritative sources confirm that Base mainnet uses chain ID 8453.",
    "observedAt": "2026-01-01T00:00:00Z",
    "provenance": {},
    "atomicFacts": [],
    "limitations": [],
    "verificationId": "cv_example",
    "providerSources": []
  }
}

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How this service works

Machine-discoverable services AI agents can call and purchase autonomously.

Output

Example use cases

Journalist verifying a statistical claim

Legal compliance check on a regulatory fact

AI agent self-verification of generated output

“Before I send this to the user, verify this fact I just generated: 'The Base mainnet chain ID is 8453' — open web sources are fine, get up to 3 sources, and tell me if anything conflicts.”

Technical details

Endpoint

POSThttps://api.aisoup.net/v1/claims/verify?utm_source=zero.xyz

When to prefer

Side effects

Claim is too vague or ambiguous for sources to confirm — returns unconfirmed status with explanation
Freshness constraint too tight — no sources found within the requested time window
All candidate domains blocked — returns error if no sources available after filtering
Claim exceeds 4000 character limit — returns 400 validation error
Minimum source threshold not met — returns result noting insufficient sources found
Payment failure via x402/MPP — returns 402 Payment Required
Rate limiting or upstream web access failure — returns 503 or timeout

Input

Schema · Request body

Field	Type	Description
asOf	—	Optional date at which the claim should be evaluated.
claim	string	The factual claim to verify.
language	string	Preferred response language or auto.
maxSources	integer	Maximum number of evidence sources to return.
jurisdiction	—	Optional country, state, or legal jurisdiction.
sourcePolicy	—	Policy controlling which kinds of web sources may be used.
allowedDomains	array	Optional hostname allowlist without schemes or paths.
blockedDomains	array	Optional hostname blocklist without schemes or paths.
freshnessHours	—	Maximum preferred source age in hours.
minimumSources	integer	Minimum number of evidence sources requested.
includeConflicts	boolean	Whether to search for and report conflicting evidence.

Output

Schema · Response

{
  "type": "json",
  "example": {
    "claim": "The Base mainnet chain ID is 8453.",
    "status": "confirmed",
    "evidence": [],
    "conflicts": [],
    "snapshots": [],
    "conclusion": "Authoritative sources confirm that Base mainnet uses chain ID 8453.",
    "observedAt": "2026-01-01T00:00:00Z",
    "provenance": {},
    "atomicFacts": [],
    "limitations": [],
    "verificationId": "cv_example",
    "providerSources": []
  }
}