{"uid":"cap_iUKHpuWg6qUPTWdETcbPs","slug":"2s-law-citation-check-062660f9","name":"2s Law Citation Check","description":"The (most) everything API: 575+ pay-per-call endpoints for AI agents — ground-truth data, a full AI gateway, and agent infrastructure (storage, queues, watchers). USDC via x402, no signup, no API keys, and upto billing: pay actual usage, not the quote.","url":"https://2s.io/api/law/citation-check?utm_source=zero.xyz","method":"POST","headers":{},"bodySchema":{"type":"object","properties":{"text":{"type":"string","description":"Legal passage to scan for case/USC/CFR citations (existence check)."},"quotes":{"type":"array","items":{"type":"object","required":["citation","quote"],"properties":{"quote":{"type":"string","description":"The text attributed to that case."},"citation":{"type":"string","description":"Case citation, e.g. \"Marbury v. Madison, 5 U.S. 137 (1803)\"."}}},"description":"Explicit quote checks: each { citation, quote } verifies the citation exists AND the quote appears in its opinion."}}},"responseSchema":null,"example":{"request":{"text":"The foundational principle of judicial review was established in Marbury v. Madison, 5 U.S. 137 (1803), where the Court held that it is emphatically the province and duty of the judicial department to say what the law is. Additionally, 42 U.S.C. § 1983 provides a civil remedy for constitutional violations.","quotes":[{"quote":"It is emphatically the province and duty of the judicial department to say what the law is.","citation":"Marbury v. Madison, 5 U.S. 137 (1803)"}]},"response":{"data":{"ok":true,"meta":{"summary":{"total":3,"verified":3,"unverified":0,"quotesChecked":1,"quotesMissing":0,"quotesPresent":1}},"items":[{"url":"https://www.courtlistener.com/opinion/84759/marbury-v-madison/","type":"case","error":null,"quote":null,"title":"Marbury v. Madison","detail":{"year":1803,"court":null,"docketNumber":null,"citationCount":5993},"exists":true,"citation":"5 U.S. 137"},{"url":"https://uscode.house.gov/view.xhtml?req=granuleid:USC-prelim-title42-section1983","type":"usc","error":null,"quote":null,"title":"Civil action for deprivation of rights","detail":null,"exists":true,"citation":"42 U.S.C. § 1983"},{"url":"https://www.courtlistener.com/opinion/84759/marbury-v-madison/","type":"case","error":null,"quote":{"note":null,"checked":true,"present":true},"title":"Marbury v. Madison","detail":{"year":1803,"court":null,"docketNumber":null,"citationCount":5993},"exists":true,"citation":"Marbury v. Madison, 5 U.S. 137 (1803)"}],"total":3,"source":{"url":"https://www.courtlistener.com/","license":"Underlying corpora are US public domain; CourtListener is the case index.","provider":"CourtListener (Free Law Project) + US OLRC + eCFR"}},"meta":{"cost":{"usd":0.0072,"tier":0},"caller":"x402","version":null,"endpoint":"law.citation-check","settlement":{"txHash":"0x89278f0eef4137e30c6ef8022dbb09bc2ffe40207a495930235b309e1c821617","network":"eip155:8453","success":true}}}},"exampleRequest":{"text":"The foundational principle of judicial review was established in Marbury v. Madison, 5 U.S. 137 (1803), where the Court held that it is emphatically the province and duty of the judicial department to say what the law is. Additionally, 42 U.S.C. § 1983 provides a civil remedy for constitutional violations.","quotes":[{"quote":"It is emphatically the province and duty of the judicial department to say what the law is.","citation":"Marbury v. Madison, 5 U.S. 137 (1803)"}]},"tags":["x402"],"displayCostAmount":"0.0072","displayCostAsset":"USDC","priceDynamic":false,"priceHint":null,"priceStatus":"priced","priceSource":"settled","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":"$0.0072/call","primary":{"kind":"static","protocol":"x402","network":"base","amountUsd":"0.018","per":"call","confidence":"exact"},"accepted":[{"kind":"static","protocol":"x402","network":"base","amountUsd":"0.018","per":"call","confidence":"exact"}]},"paymentMethods":[{"uid":"pm_JURj0PxF7J6LP8TRDlT6d","protocol":"x402","methodType":"crypto","chain":"base","mode":"charge","costAmount":"0.018","costPer":"request","priority":0,"asset":"0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913","unit":"request","depositMicros":null,"planRef":null}],"brandName":null,"brandSlug":null,"brandBaseUrl":null,"brandDocsUrl":null,"whatItDoes":"Verifies that legal citations (case law, USC, CFR) exist and optionally confirms that quoted text actually appears in the cited opinion","exampleAgentPrompt":"Can you verify these citations from the legal memo I'm reviewing? Check that 'Brown v. Board of Education, 347 U.S. 483 (1954)' exists, that '42 U.S.C. § 1983' is real, and confirm that the quote 'separate educational facilities are inherently unequal' actually appears in the Brown opinion.","exampleUseCases":null,"resultDescription":"Returns a structured result for each citation: whether it exists (boolean), the title and court metadata (year, court, docket number, citation count), a URL to the source opinion, and — for explicit quote checks — whether the quoted text was found in the opinion. A summary object totals verified vs. unverified citations and quote presence/absence counts.","failureModes":["Citation not found in CourtListener or OLRC index — exists=false returned","Quote provided but does not appear in the opinion — quotesPresent count unchanged, quoteMissing incremented","Malformed citation string that cannot be parsed — error field populated on that item","Network or upstream source unavailability — non-200 or partial results","Payment failure via x402 — request not processed"],"whenToPreferThis":"Use this endpoint when you need ground-truth verification of legal citations — especially to detect AI hallucinations in generated legal text. It covers case law (via CourtListener), US Code (USC), and CFR citations in one call, and can additionally confirm whether a specific quoted passage appears in the actual opinion. Prefer it over general web search when you need a deterministic exists/not-exists answer backed by authoritative legal corpora rather than a web snippet.","instructions":null,"reviewSummary":null,"reviewSummaryHighlights":null,"reviewSummaryConcerns":null,"reviewSummaryGeneratedAt":null,"activationCount":0,"lastUsedAt":null,"lastSuccessfullyRanAt":null,"lastHealthCheckAt":"2026-10-10T00:59:04.826Z","isFirstParty":false,"canonicalSlug":"2s-law-citation-check-062660f9"}