Give your AI the letter of the law.
Access Brazilian legislation and case law directly in ChatGPT or Claude, with verified validity and direct links to the official source.
- STF, STJ, TST, and more
- 27 state courts
- 2,400+ statutes
The hallucination problem
Your AI can't be trusted.
Ask an AI assistant for a precedent that says what you want to hear, and it might invent a full ruling, complete with a case number, a court, and a holding. It reads like a real citation, but it isn't.
A citation that isn't there
AI assistants create fake citations with confidence. Brazilian courts have already fined lawyers over it, some referred to the OAB's ethics council.
Superseded precedents
A ruling might have been correct for years, until a higher court reversed it. The AI has no way to know, because the change lives in the relationship between the two decisions, not in the text it read.
Yesterday's law
New laws take effect, and resolutions and regulations are published in the Official Gazette, but the AI has no reliable access to any of it.
The solution
How we solve it.
We hand your AI assistant the literal text of laws and precedents, connected to other legal texts, with validity and date mapped.
You describe the legal facts to the AI.
Official sources
With Letra da Lei, the AI doesn't rely on its own memory. It looks up the official text, from the article to the full ruling, always with links so you can verify the source.
Temporal validity
Relationships between precedents are mapped, and validity is checked against your case's fact date, catching a ruling that only applies going forward.
Always current
We curate what matters most straight from official sources, like the STJ, STF, and state courts' portals, and the Diário Oficial, as soon as it takes effect.
Available now
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federal statutes indexed by article
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case-law sources
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jurisdictions with indexed case law
How it works
No switching tools.
You don't leave ChatGPT or Claude to do legal research. Describe what you need, and Letra da Lei brings the most relevant law or precedent, based on official sources.
Built for the AI you already use
- ChatGPT
- Claude
What you're probably wondering.
How do I get started?
Add Letra da Lei to your assistant in just a few steps. It's free.
See the docsWhere does the data come from?
From official sources: Planalto.gov.br for legislation, and the STJ, STF, and other courts' portals for case law, indexed at the article level with effective-date metadata. We don't use third-party summaries or non-institutional sources.
How do you make sure a law or precedent is still in force?
Every search returns the current text, straight from our database. Our team curates the data to keep it always up to date and valid. See how it works on our accuracy page.
Does it cover case law and state laws?
Federal and state case law are already live, alongside federal legislation indexed by article. State and municipal legislation are on the roadmap. See the coverage page for the full list.
Which AI assistants does it work with?
Today, ChatGPT and Claude (web and desktop). Letra da Lei is the first Brazilian legal plugin listed in ChatGPT's official app directory. Other MCP-compatible assistants should follow as they roll out support.
Start for free
Give your AI the letter of the law.
Install Letra da Lei to access Brazilian legislation and case law directly in ChatGPT or Claude.