A (free!) Legal Connector that Gets Out of the AI’s Way.
DingDuff is a Claude MCP connector for legal research. It links your existing Claude account to a database of millions of legal opinions, state and federal statutes, and court filings from around the country.
We’ve designed DingDuff to be simple, useful, and inexpensive to run, which allows us to currently operate it with a tip jar. All our effort has gone into one thing: building a tool we actually use in our own daily work. That meant making it run seamlessly inside Claude. We don’t dress it up in fancy packaging or try to tell the AI how to do its job. Our goal is to empower Claude to do what we ask, then get out of its way — and we’ve found the results to be quite brilliant when we do.
What lawyers are saying
“DingDuff is a must-have for every litigator. Instead of spending hours devising Westlaw search terms, I can now get legal research through plain English prompts, just like working with an associate. I recently filed a thoroughly researched Ninth Circuit opening brief with DingDuff—without once opening Westlaw. It simply wasn’t needed.”
“DingDuff is a game changer and I honestly can’t imagine practicing without it. It has completely changed legal research for me from a slog to something I can complete in minutes. Even after spending hours doing research I was always worried I was missing something. And Westlaw’s AI, while helpful, is still regularly incomplete or inaccurate. DingDuff is giving me confidence in my ability to do legal research quickly and thoroughly, and I use it daily in my practice. I also regularly get partner feedback that they are blown away by the research memos I put together using DingDuff and Claude. I can’t imagine going back to a world without it.”
Legal Sources in DingDuff
More About DingDuff
DingDuff started as a side project by two practicing lawyers — us, Kyle and Stephanie — who wanted something we could use at work in our own day jobs. We were never trying to build a company.
What we didn’t expect was to get an answer to an empirical question that we hadn’t even thought to ask: does a purpose-built legal AI platform (like Westlaw’s AI/Deep Research) actually perform better than a frontier AI model (like Claude Opus) that has been given direct access to the legal sources?
In our hands, DingDuff was outperforming our firms’ Westlaw AI accounts so consistently that we both eventually stopped using them. That’s when we decided to make DingDuff available to other lawyers.
Who Is DingDuff For?
DingDuff is for lawyers. The reason DingDuff works so well is because we haven’t tried to program a bunch of guardrails into it, or teach Claude how to lawyer. But that same hands-off design means Claude + DingDuff will occasionally get something wrong (although we have never seen it hallucinate a fake case or statute).
With DingDuff, the lawyer reading and checking the output acts as the guardrail. That’s why having a lawyer-user is essential, and the reason we’re making DingDuff available only to lawyers.
By signing up for and using DingDuff you accept the Terms of Service, which includes a promise that you’re a lawyer.
Get DingDuff
You need two things to get started: (1) your own Claude plan and (2) a username/password for the DingDuff “connector.”
1 Sign Up for DingDuff
2 Install DingDuff
DingDuff is listed in Claude’s connector directory, so there’s nothing to paste and nothing to configure. Open the listing, click the + to add it, and sign in with the DingDuff account you just created:
Prefer to find it yourself? In Claude, go to Customize → Connectors → + → Browse connectors, then search DingDuff and click the + on its card.
Want Claude to walk you through the whole setup — connector, skills, and settings? Open Claude and paste this:
Or follow the illustrated step-by-step setup instead.
For those who want to feel like part of the project, we have a public GitHub repo here: github.com/DingDuff/dingduff-public/wiki Feel free to post issues in our public GitHub, as well.
How DingDuff works
DingDuff works wherever Claude does — and it adapts to where you’re running it.
DingDuff is at its best in Claude Cowork, where Claude can reach a folder on your computer.
Instead of pulling opinions into the chat, it saves your own full copy of each opinion to a desktop folder so that you can revisit them later.
DingDuff can run right inside Claude’s web app and mobile app. Because Claude can’t save files to your device here, you’ll have to make sure the virtual machine feature is turned on in your Claude settings.
To do this, go to your Claude account → Settings → Capabilities. Scroll down and turn on two features: “Claude code execution and file creation” and “Allow network egress.”
DingDuff works on its own, but our free skills make its answers noticeably better. The easiest way to get them — and to stay on the current versions — is our plugin, which installs all our skills at once.
- In Claude, open Customize → the Plugins tab.
- Under Personal plugins, click + → Add marketplace → Add from a repository.
- Enter
https://github.com/DingDuff/dingduff-public. - Click Install on the DingDuff plugin.
Works in Cowork, the desktop app, and claude.ai in a browser. When
we ship a new version of a skill it comes through the marketplace,
so you don’t have to come back here and re-download each file
yourself. In Claude Code, do the same thing with
/plugin marketplace add DingDuff/dingduff-public then
/plugin install dingduff@dingduff.
What’s in the plugin — and, if you’d rather pick and choose, each skill as a single-file download you upload to Claude yourself:
The skills are released under the DingDuff Skills License 1.0. Use them in your paid work without restriction, change them to suit your practice, and keep everything you produce with them. The conditions apply only if you pass a skill on to someone else.
End-to-end legal research — finds, retrieves, reads, and validates the controlling cases, statutes, and regulations, maps the citation network and statutory landscape, and confirms everything is still good law. Scales from a quick “what’s the law on X” to a full doctrinal map.
New in v2.5 — two-tier validation. Every case gets a quick screen; the cases your argument actually rests on get handed to the full Validity Check skill. Claude weighs how load-bearing each case is against the cost of the deep check, and then tells you which cases got which. A quick screen is a smoke test, not a verification, and the answer says so instead of letting the two look alike.
DingDuff works without it, but it works a lot better with it: this skill carries the research method and the bulk of our anti-hallucination instructions, which we can’t push through the connector itself. If you install only one, install this one.
Reasoning engine — frames the issues, synthesizes the governing rule, analyzes the facts against it, organizes the proof (CRAC/CREAC), and deploys authority. Use before drafting any memo, brief, motion, or letter.
Before an argument rests on a case, confirms the case is still good law for the proposition you’re citing it for — tracing its appellate history, sweeping forward for opinions that overruled or narrowed it, and checking the authorities the case itself leaned on. Returns a verdict with its confidence and an honest statement of what it could not see.
After you draft a memo (Markdown, Word, or Google Docs), verifies every citation against your stored opinions and statutes plus any other sources you supply, checks that each highlighted passage is the on-point part of the source, then opens an interactive attorney review panel and records your verdicts.
Formats citations the way courts expect — signals, pincites, short forms (id./supra), string cites, and same-matter filings.
Once a skill is in your skill library, you mostly don’t have to think about it. Claude is built to automatically grab and implement the skills from your skill catalog that Claude identifies as best suited to the task you’re asking it to accomplish.
Because of this, Claude will nearly always reach for the Legal Research skill on its own while using DingDuff. But if you want to be sure it does (this skill carries the most anti-hallucination instructions) select it manually with the “+” (the skill picker) in your chat window.
The Legal Analysis skill is optional and builds in a structured CREAC/IRAC method. If you ask Claude specifically to draft a memo, it will likely grab this skill. But if you want to ensure it does, also add it with the “+” sign in the chat window. (Again, this skill is optional: while Kyle likes to use this skill, Stephanie almost never uses it.)
Validity Check is the one to reach for when an argument is about to rest on a particular case. If you have Legal Research installed it calls this skill on its own, on the cases it judges load-bearing, and reports which cases got the deep check and which only got a screen. You can always ask for it by name — “check whether Smith is still good law for that proposition” — or ask for a specific case to be checked the hard way. It runs in a subagent, so your main chat stays fast while it works.
Citation Check and Legal Citation Format only run when you specifically ask for them. If you select Citation Check with the “+” before Claude drafts a memo or brief it will produce both the draft and a companion cite-check file; or you can run it on its own to cite-check a memo or brief already saved in your desktop folder. The same goes for the Legal Citation Format skill.
Costs — Tip Jar
DingDuff is free. But we do have some costs in running it. Thankfully our costs are low enough that we can be supported through a tip jar. If you find DingDuff helpful and would like to help keep it free, please consider donating.
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Meet the Team
Like most lawyers these days, we (Kyle and Stephanie) felt acutely the twin fears that (a) the robots would eventually replace us, and (b) in the meantime, the other lawyers would get a better robot and use it against us. So before Westlaw AI even existed, and anticipating that other lawyers would soon have some sort of AI death star we'd have to confront, we began developing our own tool for our own use.
For a year, we've made iterative improvements. DingDuff began as a scrappy interface to a database we had compiled locally, running on a Raspberry Pi tucked away in Kyle's closet. But it has since grown into something far more capable—a powerful legal tool that runs through several databases, including CourtListener** and state and federal statutes. And after two years of dreading the inevitable Westlaw death star, we discovered a happy accident: our homegrown tool works comparably well, and often better in our opinion.
Finding ourselves unexpectedly in possession of an incredibly useful legal tool with significant potential, we wanted to share it with our lawyer friends. To help turn DingDuff from a personal project into a shareable product, we brought on two software developers: Jeremy, a longtime friend from our undergraduate philosophy days at UT Austin, and Julia, a recent computer science graduate.
**This entire project would never have been possible without the data heroes at CourtListener.
Kyle is a mass torts lawyer with a passion for history, philosophy, the law, and everything Reddit. He has served as first or second chair in more than two dozen trials and written and argued appellate briefs before the Texas Supreme Court and federal courts of appeals. Kyle grew up in Austin in a family of engineers and lawyers and is a proud double longhorn (both undergrad and law school) and the main architect behind DingDuff.
Stephanie is a commercial litigator with a background in financial regulation and litigation. Since law school, she has practiced in private firms, served in the federal government, clerked for a federal judge, and taught legal research and writing at Georgetown Law. She grew up in the Austin area in a family of engineers, scientists, and one very skilled carpenter. She has her undergrad degree from UT and her law degree from Columbia Law School.
Julia is a talented software developer who is always finding ways to pair her computer science degree from Texas A&M with her passion for art and design. Julia also grew up in the Austin area.
Brady has always been an engineer and problem-solver by nature. After undergrad and before contributing to building DingDuff, Brady helped run the nuclear operations onboard a naval submarine.
George is Stephanie's dog and the DingDuff fetcher of legal sources.
Contact Us
Have a question, feedback, or just want to say hello? We'd love to hear from you.
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