{"uid":"cap_ec4kR_LGIi0RxyWZ0TAkI","slug":"web-evidence-api-claim-verification-with-cited-sources-ad5d2259","name":"Web Evidence API – Claim Verification with Cited Sources","description":"Machine-discoverable services AI agents can call and purchase autonomously.","url":"https://api.aisoup.net/v1/claims/verify/research?utm_source=zero.xyz","method":"POST","headers":{},"bodySchema":{"type":"object","properties":{"asOf":{"type":["string","null"],"format":"date","description":"Optional date at which the claim should be evaluated."},"claim":{"type":"string","maxLength":4000,"minLength":3,"description":"The factual claim to verify."},"language":{"type":"string","description":"Preferred response language or auto."},"maxSources":{"type":"integer","maximum":20,"minimum":1,"description":"Maximum number of evidence sources to return."},"jurisdiction":{"type":["string","null"],"description":"Optional country, state, or legal jurisdiction."},"sourcePolicy":{"enum":["official_only","authoritative","open_web"],"description":"Policy controlling which kinds of web sources may be used."},"allowedDomains":{"type":"array","items":{"type":"string"},"description":"Optional hostname allowlist without schemes or paths."},"blockedDomains":{"type":"array","items":{"type":"string"},"description":"Optional hostname blocklist without schemes or paths."},"freshnessHours":{"type":["integer","null"],"maximum":8760,"minimum":1,"description":"Maximum preferred source age in hours."},"minimumSources":{"type":"integer","maximum":10,"minimum":1,"description":"Minimum number of evidence sources requested."},"includeConflicts":{"type":"boolean","description":"Whether to search for and report conflicting evidence."}}},"responseSchema":{"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":[]}},"example":null,"exampleRequest":null,"tags":["x402"],"displayCostAmount":"0.25","displayCostAsset":"USDC","priceDynamic":false,"priceHint":null,"priceStatus":"priced","priceSource":"probe","requiresHandshake":false,"reviewCount":0,"rating":{"score":"0.00","successRate":"0.00","reviews":0,"stars":null,"state":"unrated"},"availabilityStatus":"unknown","priceObserved":null,"sessionDeposit":null,"pricing":{"kind":"static","summary":"$0.25/call","primary":{"kind":"static","protocol":"x402","network":"base","amountUsd":"0.25","per":"call","confidence":"exact"},"accepted":[{"kind":"static","protocol":"x402","network":"base","amountUsd":"0.25","per":"call","confidence":"exact"}]},"paymentMethods":[{"uid":"pm_Q9wlOBTEhPBMz0EF4fOfp","protocol":"x402","methodType":"crypto","chain":"base","mode":"charge","costAmount":"0.25","costPer":"request","priority":0,"asset":"0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913","unit":"request","depositMicros":null,"planRef":null}],"brandName":null,"brandSlug":null,"brandBaseUrl":null,"brandDocsUrl":null,"whatItDoes":"Verifies a natural-language claim against web sources, returning a verdict, cited evidence, source snapshots, and cryptographic provenance hashes","exampleAgentPrompt":"Can you verify the claim that 'The Eiffel Tower is 330 meters tall including its antenna' using only authoritative sources, pull at least 2 sources, and include any conflicting information you find?","exampleUseCases":[{"title":"Fact-checking a news headline","prompt":"Can you verify the claim 'The US inflation rate dropped below 3% in June 2024'? Use authoritative sources only, find at least 3 sources, limit to the US jurisdiction, and include any conflicting reports you find."},{"title":"Validating a blockchain technical spec","prompt":"Please verify the claim 'Base mainnet uses chain ID 8453' against official sources — I want at least 2 sources confirmed within the last 720 hours so I know the info is fresh."},{"title":"Checking a competitor's product claim","prompt":"I need you to fact-check the claim 'Company X's product has 99.99% uptime guaranteed' using open web sources, up to 10 sources, and flag any conflicts or contradictions you come across."}],"resultDescription":"A JSON object containing: a verdict status (e.g. confirmed, refuted, uncertain), a natural-language conclusion, an array of evidence citations with URLs and excerpts, conflicting source entries, web snapshots with hashes for provenance, atomic facts extracted from sources, a unique verificationId, a timestamp of observation, and any noted limitations of the research.","failureModes":["Claim text too short (< 3 chars) or too long (> 4000 chars) returns validation error","Insufficient sources found matching policy returns uncertain status with limitations noted","Blocked or restricted domains prevent sourcing, reducing evidence quality","freshnessHours constraint too tight may yield no qualifying sources","Payment failure via x402/MPP returns 402 before research begins","Ambiguous claims without enough context may return low-confidence or inconclusive results"],"whenToPreferThis":"Choose this endpoint when you need verifiable, cited, source-backed fact-checking with cryptographic provenance rather than a simple LLM opinion. It is especially valuable when jurisdiction-specific, freshness-constrained, or domain-restricted evidence is required, or when you need conflict detection across sources. Prefer it over generic web search when the output must be auditable and traceable with snapshot hashes.","instructions":null,"reviewSummary":null,"reviewSummaryHighlights":null,"reviewSummaryConcerns":null,"reviewSummaryGeneratedAt":null,"activationCount":0,"lastUsedAt":null,"lastSuccessfullyRanAt":null,"lastHealthCheckAt":"2026-10-13T06:46:22.993Z","isFirstParty":false,"canonicalSlug":"web-evidence-api-claim-verification-with-cited-sources-ad5d2259"}