CourtListener

What it is

CourtListener is the free US case-law and federal-docket database run by Free Law Project, a nonprofit formed in 2013. It holds more than nine million decisions from over 2,000 courts — Free Law Project reports coverage of more than 99.9% of precedential US case law as of 2023 — plus the RECAP Archive of tens of millions of PACER filings, federal appellate oral-argument recordings, and federal judges’ financial disclosures. Anyone can search it in a browser without paying.

The part that matters for legal AI is not the website. On 12 May 2026 Free Law Project put the whole platform behind a hosted MCP server at https://mcp.courtlistener.com/, signed into with an ordinary CourtListener account over OAuth. It is listed in the Claude connector directory, in ChatGPT, and since 25 August 2026 inside Google Cloud’s Gemini Enterprise for Legal, next to Thomson Reuters, Harvey and Everlaw. Claude Code users add it with one command:

claude mcp add --transport http courtlistener https://mcp.courtlistener.com/

The server exposes dedicated tools for search, citation verification and alerts, and reaches the rest of the REST API through two generic tools, get_endpoint_schema and call_endpoint.

Why it shows up in Legal Ops stacks

• It is the free grounding layer for a general-purpose assistant. A Claude or ChatGPT deployment with no research connector answers case-law questions from model recall. Attaching CourtListener gives it retrieved opinions with links back to the source, at zero licence cost and with no procurement path to walk. That is why Claude for Legal lists it among its research connectors.
• The citation lookup is purpose-built to catch hallucinated cites. Paste a brief and the API parses every citation with Free Law Project’s Eyecite parser and matches it against 18,136,506 citations. Each one comes back as found (200), valid but not in the database (404), unknown reporter (400), or ambiguous (300). A fabricated case usually lands in 404 — the cue to pull the reporter before filing. Our citation-verification Claude skill uses it as a named provenance source.
• PACER without the per-page meter, where someone already paid. RECAP documents are copies that other users bought and the RECAP extension uploaded. When the filing you need is already there, retrieval costs nothing.
• Alerts run on the same account. Docket alerts and opinion search alerts let an agent, or a paralegal, watch a case or a doctrine without a Westlaw or Lexis seat.

Pricing reality

The account is free, and so is API access — at a low ceiling. Since 7 May 2026, a non-member account gets 5 API calls per minute, 50 per hour and 125 per day; before that change every user got 5,000 per hour. Accounts that had already made 1,000+ requests kept their old rate. The MCP server draws on the same quota.

Higher limits come from a Free Law Project membership:

Group memberships run from $30 a month (Tier 1, up to five people) to $2,500 a month (Tier 4, up to 100). EDU memberships are free with a .edu address, and since June 2026 US nonprofit legal-aid organisations get a free group membership at Tier 1 limits. Free Law Project scopes membership API access to small firms, small public bodies, legal-aid groups, small media, academics and pre-revenue organisations; larger or funded companies are directed to a commercial agreement, which is quote-only.

The comparison that decides most evaluations: a Tier 4 membership at $1,000 a year costs less than one Midpage seat at $1,200 a year, and roughly a fifth of a Westlaw Precision with CoCounsel seat at about $428 a month.

Best for

Solo litigators, small firms, legal-aid organisations and in-house teams that already run Claude or ChatGPT and need a free, defensible way to retrieve US federal and state case law and confirm that every citation in a draft exists. It is also the right first connector for a legal-ops team piloting legal MCP before any paid research contract is signed.

Alternatives and when to pick them

• Thomson Reuters CoCounsel with Westlaw — the market-share leader. Pick it when you need KeyCite treatment, secondary sources and practice notes, or when a court or carrier expects Westlaw by name.
• LexisNexis Protégé — the other incumbent. Pick it when Shepard’s and an existing Lexis enterprise agreement make the AI layer a marginal cost.
• Harvey — the fastest-growing entrant in legal AI. Pick it for firm-wide drafting and advisory work; it is a platform, not a data source.
• Midpage — the closest paid sibling, also sold as an MCP connector. Pick it when you need a treatment citator, statutes and regulations, and no daily call cap.
• Trellis — pick it when the matter turns on state trial-court dockets and judge analytics, which CourtListener does not centre on.

Watch-outs

• There is no citator. CourtListener tells you a case exists and what cites it; it does not flag that a case was reversed or overruled. Guard: run every authority you actually cite through KeyCite, Shepard’s or Midpage before filing, and keep CourtListener for retrieval and existence checks.
• Citation lookup confirms existence, not accuracy. It does not check quoted language, and it skips statutes, law-review cites, “id.” and “supra”. A real case cited for a proposition it never held passes as 200. Guard: require a human to open the linked opinion for every quote and pin cite in the final draft.
• The free tier runs out mid-session. An agent that searches, reads opinions and follows citation networks makes several calls per question, and 125 a day goes fast. Guard: watch the usage counter on your CourtListener profile during a one-week pilot, then buy the tier that covers your peak day before rolling it out.
• Commercial use sits outside membership. A funded company embedding CourtListener in a product it sells is not what a $100-a-month membership covers. Guard: email Free Law Project for a commercial agreement before shipping, and use the bulk data files or database replication service for volume work.
• RECAP has gaps. It holds only the PACER documents someone has already bought. Guard: treat a missing filing as “not yet in RECAP”, not “does not exist”, and budget PACER fees for the documents you must have.

For the surrounding category, see best MCP tools for legal ops, best legal citation checking tools and grounding vs hallucination in legal AI.