@pipeworx/court-listener

Connect: https://gateway.pipeworx.io/court-listener/mcp · Install: one-click buttons

Tools: 6

Free Law Project’s CourtListener. Federal and state court opinions, oral argument recordings, judge biographies, PACER filings (where covered). The largest free, structured database of US case law — used by lawyers, journalists, researchers. Free, no auth (rate-limited; key recommended for higher volume).

Why this matters for AI agents

For legal research, case-law citations, or “did this issue come up in court?” questions, CourtListener is the right starting point. Where Westlaw and Lexis charge thousands per seat, CourtListener provides searchable opinions for free. Coverage is excellent for federal courts and growing for state courts.

Common flows:

• Opinion search. “Cases involving Section 230 immunity” → keyword + jurisdiction filter.
• Specific opinion. Full text of a court opinion by ID or citation.
• By judge. “Cases authored by Justice Kagan” → search by author + court.
• Oral arguments. Audio recordings (where available) with metadata.

Auth

Free, but unauthenticated calls are heavily rate-limited (~5,000/day per IP). Get a free API token from https://www.courtlistener.com/help/api/rest/ for higher rates. Pass via _apiKey.

Coverage

For “what’s the law on X?” the supreme courts and circuit courts are usually what matters; trial-court opinions are less precedential.

Common pitfalls

• Citation format. US case-law citations follow Bluebook conventions: Roe v. Wade, 410 U.S. 113 (1973). CourtListener’s IDs differ from these; use the cluster_id or slug fields for stable references.
• Published vs unpublished. Federal courts mark opinions “published” (precedential) or “unpublished” (binding only on parties). Unpublished doesn’t mean unimportant — many recent significant opinions stayed unpublished. Don’t filter to “published” without thought.
• Citation network. CourtListener tracks “cited by” and “cites to” relationships. Use them for impact analysis (“which Supreme Court opinions have shaped this doctrine?”).
• PACER limitations. The full PACER (federal trial-court filings) corpus is paywalled. CourtListener has a partial mirror via the RECAP project, donated by users. Coverage is opportunistic, not comprehensive.
• State coverage is uneven. Don’t assume “no opinion found in CourtListener” means “no opinion exists” — especially for state appellate cases. Cross-reference with state-court websites or commercial databases for completeness.
• Search is keyword + cluster, not full text. Long-tail queries like specific phrasings may underperform. Use CL’s ”+ exact phrase” syntax when precision matters.

Tools

• search_opinions — Search US court opinions by keyword (e.g., “qualified immunity”, “Fourth Amendment”). Covers federal and state courts. Each result carries the case name, court, filing date, docket number, official ci
• search_dockets — Search US court dockets by keyword. Covers PACER and RECAP archives. Each result carries docket_id, case name, court, filing and termination dates, docket number, nature of suit, the cause of action,
• find_case — Find a US court case BY NAME and get its citations, filing date, judges and how often it has been cited. Searches 8.3 million opinions across 3,361 courts from our hosted mirror of CourtListener — no
• lookup_citation — Resolve a US reporter citation such as “410 U.S. 113” or “347 U.S. 483” to the case it refers to, with name, filing date, judges and citation count. Reads our hosted CourtListener mirror — no API key.
• list_case_opinions — List every opinion filed in one case (cluster) — majority, concurrences and dissents — with the opinion_id needed to read each one via get_opinion. Reads our hosted CourtListener mirror; no API key. U
• get_opinion — Get the FULL TEXT of a US court opinion by its CourtListener opinion ID (the opinion_id returned by search_opinions). Served from our hosted mirror of CourtListener bulk data — 8.3 million opinions, 7