Lawful MCP

English | 한국어

Korean case law, statutes and sentencing data as MCP tools. Point an AI client at it and the model can look up statute text as it stood on a given date, find judgments by the facts of a case, read one judgment and answer a question about it, and compute a sentencing range the way a Korean court does.

Five read-only tools:

This is the production system behind 로풀 (Lawful), a free Korean legal-AI service, and the descendant of the research prototype in legal_mcp — see Paper.

Quick start — hosted

The full corpus (220k+ judgments, statutes with their amendment history, administrative rules, sentencing guidelines) is served for you. No rate limits. Three ways in:

Claude / ChatGPT on the web — no code. Add a custom connector with this URL, sign in with OAuth when asked, and the five tools appear. No API key needed:

https://mcp.crow-tit.com/mcp

Step-by-step with the exact menu clicks: crow-tit.com/docs#mcp

Claude Code — one command, with a free key from console.crow-tit.com:

claude mcp add --transport http lawful https://mcp.crow-tit.com/mcp \
  --header "Authorization: Bearer ct_..."

Any other MCP client (Claude Desktop, Cursor, …) — JSON config, same key:

{
  "mcpServers": {
    "lawful": {
      "url": "https://mcp.crow-tit.com/mcp",
      "headers": { "Authorization": "Bearer ct_..." }
    }
  }
}

Related MCP server: Korean Law MCP

Quick start — self-host

The repository ships a sample corpus so a clone runs immediately:

git clone https://github.com/LimEulYoung/lawful-mcp
cd lawful-mcp
pip install -e .
lawful-mcp                 # stdio
lawful-mcp --transport http --port 8100

Register it with a client:

{
  "mcpServers": {
    "lawful-mcp": {
      "command": "lawful-mcp"
    }
  }
}

Configuration is all environment variables — see .env.example. Nothing is required; the defaults use the bundled corpus.

The dive tool needs a model

Four of the five tools are pure database reads. precedent_dive sends one public judgment body to a language model and asks it to extract an answer, so it needs an endpoint:

export DIVE_API_KEY=...
export DIVE_BASE_URL=https://api.openai.com/v1   # any OpenAI-compatible endpoint
export DIVE_MODEL=...

Without those three the tool is not registered and the other four run normally.

The corpus

The tools read one SQLite file. What ships here is a bounded sample, not the whole thing:

The sample is enough to exercise every tool and run the tests. For real work, use the hosted corpus.

Search combines two lexical indexes: a character-trigram FTS and a morpheme FTS built with Kiwi, fused with reciprocal rank fusion. The morpheme index is not an optimisation — Korean charge names are often two characters (사기, 절도, 폭행), and a trigram index cannot form a trigram from two characters, so those queries return nothing without it.

Judgments are non-copyrightable under Article 7 of the Korean Copyright Act. Court and case-number provenance is preserved in the data.

Building your own

scripts/build_sample_db.py carves a sample out of a full corpus and is also the reference for the schema — which tables the tools read, how the full-text indexes are built, and how statute versions resolve:

python scripts/build_sample_db.py --source /path/to/corpus.db \
    --dest my_sample.db --cases 5000 --statutes all

Paper

The retrieval and tool-use design was evaluated on the Korean Bar Examination:

Agentic RAG for Legal Question Answering in Civil Law: Evidence From the Korean Bar Examination Eul Young Lim and Jihun Park IEEE Access, vol. 14, pp. 124441–124458, 2026. doi:10.1109/ACCESS.2026.3722717 — open access

Benchmark code, questions and per-model results are archived in legal_mcp. If you use this tool in research, please cite the paper (CITATION.cff).

Also available

• Lawful Agent API — one question in, a grounded answer out. crow-tit.com

• 로풀 (Lawful) — the free consumer service, 법률AI: chat, search, labour calculators, legal document drafting. lawful.crow-tit.com

Notes

This is a search tool over public legal sources, not legal advice. What it returns is source material and statistics; deciding what they mean for a particular matter is a lawyer's job.

Development happens in a private repository and lands here in batches, so issues are welcome but pull requests may be merged by hand rather than through the button.

MIT licensed.