Legal citation and quotation verifier (US case law)

$1.50 USDC per call · Legal and patents · POST /api/v1/legal-cite-verifier · Id legal-cite-verifier

Extracts US reporter citations from a brief (U.S., S. Ct., L. Ed., F., F.2d, F.3d, F.4th, F. Supp., state and regional reporters) and checks each against Harvard's Caselaw Access Project and, when the operator has configured a token, the CourtListener Citation Lookup API. Reports FOUND, MISMATCH (case name, year or circuit differs), NOT_FOUND, AMBIGUOUS, or UNCHECKED with the reason, and never marks an unchecked citation FOUND. Quotations are searched in the cited opinion with deterministic matching and every normalization is listed. Statutes, id., supra and Westlaw/Lexis cites are reported as UNCHECKABLE_TYPE. Without a CourtListener token the result is partial for volumes outside CAP (roughly pre-2019). The optional proposition check is off by default and can only point at a verified passage. Not legal advice.

What you get

A fabricated or misquoted authority in a filing can bring sanctions and a disciplinary referral; this gives a signed per-citation record with source hashes to attach to a pre-filing check.

Call it

Send the JSON body below to https://agents.writerslogic.com/api/v1/legal-cite-verifier. An unpaid request answers 402 with the price and how to pay; a request that fails with a 5xx status is not charged.

curl -i -X POST https://agents.writerslogic.com/api/v1/legal-cite-verifier \
  -H 'content-type: application/json' \
  -d '{"text":"Plaintiff'\''s position follows from Brown v. Board of Education, 347 U.S. 483, 495 (1954) (\"Separate educational facilities are inherently unequal.\"). Defendant'\''s liability under the Montreal Convention is established by Varghese v. China Southern Airlines Co., Ltd., 925 F.3d 1339 (11th Cir. 2019).","quotes":[{"citation":"347 U.S. 483","quote":"Separate educational facilities are inherently unequal."}]}'

Input

Field	Type	Required	Description
`text`	string; length 1..64000	no	Brief or memo text. Citations and their case names, court and year are extracted from it.
`citations`	array<string; length 3..300>; max 60 items	no	Citations to check instead of, or in addition to, text.
`quotes`	array<object>; max 40 items	no	Quotations to find verbatim in the cited opinion.
`check_propositions`	boolean	no	Default false. Runs one optional model call that may only point at a verified passage.
`propositions`	array<object>; max 10 items	no
`max_citations`	integer; 1..40	no	Distinct reporter citations to check. Default 40.

Example request body

{
  "text": "Plaintiff's position follows from Brown v. Board of Education, 347 U.S. 483, 495 (1954) (\"Separate educational facilities are inherently unequal.\"). Defendant's liability under the Montreal Convention is established by Varghese v. China Southern Airlines Co., Ltd., 925 F.3d 1339 (11th Cir. 2019).",
  "quotes": [
    {
      "citation": "347 U.S. 483",
      "quote": "Separate educational facilities are inherently unequal."
    }
  ]
}

Result

The response is { "data": ..., "_provenance": ... }. data carries these fields; _provenance is a signed W3C Verifiable Credential with a C2PA-style manifest, checked free at POST /api/v1/verify-provenance.

Field	Type	Required	Description
`verdict`	string; one of "ISSUES_FOUND", "INCOMPLETE", "ALL_CHECKABLE_VERIFIED", "NO_CITATIONS_FOUND"	no
`confidence`	string; one of "high", "medium", "low"	no
`risk`	object	no	flagged_citations (NOT_FOUND or MISMATCH), flagged_quotes, inconclusive_items.
`next_step`	string	no
`summary`	string	no
`counts`	object	no	Citation and quote counts by status.
`citations`	array<object>	no
`quotes`	array<object>	no
`propositions`	array<object>	no
`unicode`	object	no	Hidden or lookalike characters found in the input (unicode-safety rules).
`evidence`	array<object>	no
`warnings`	array<string>	no
`manifest`	object	no	Version, input hash, data access mode (authenticated\|public\|public_fallback), token state, llm state, timing.
`limitations`	array<string>	no

Pay and connect

Available through: x402 (USDC on Base), MCP, RapidAPI, Apify.

Machine-readable

This agent as JSON (schemas, example, OpenAPI operation)
Free signed sample response
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