Korean Law MCP

42 APIs compressed into 10 tools. Search and retrieve Korean statutes, precedents, administrative rules, ordinances, treaties and legal interpretations, and verify the legal citations in AI answers — from your AI assistant or terminal.

MCP server + CLI for Korea's official legal database (법제처 Open API). Works with Claude Desktop, Cursor, Windsurf, Zed, and any MCP-compatible client.

한국어

Start in one line: add https://mcp.gomdori.app/law?oc=YOUR_KEY as a custom connector in Claude.ai, or run npx --ignore-scripts --omit=optional korean-law-mcp setup → Quick Start

One-click install for VS Code and Cursor (works without a key on a shared quota; add ?oc=YOUR_KEY to the URL for your own):

If this saves you time, a GitHub ⭐ helps others find it.

_{▶ Click to play on YouTube. Narration is in Korean.}

Connect it to your AI

Connect to Claude	Connect to ChatGPT

Recent updates

Current version v4.15.13. All numbers come from the measurements recorded in the CHANGELOG.

Earlier versions: see CHANGELOG.md. Milestones:

• v4.14.1: single-article lookup 3.1s → 0.24s (13×); a 15-citation check went from ✓0 to ✓15
• v4.13.0: compliance-register monitoring from 98 search_law calls → 1–2 search_law_bulk calls
• v4.4.0: exposed tools 19 → 9, tool-list context ~15.1KB → ~7.2KB (52% smaller)
• v3.4.0: precedent / constitutional / admin-appeal responses use 74% fewer tokens on average

Why this exists

South Korea has 1,600+ active laws, 10,000+ administrative rules, and a precedent system spanning Supreme Court, Constitutional Court, tax tribunals, and customs rulings. All of this lives behind a clunky government API with zero developer experience.

This project wraps that entire legal system into 10 tools that any AI assistant or script can call. Built by a Korean civil servant who got tired of manually searching 법제처 for the hundredth time.

Quick Start

Listed on the official MCP Registry: io.github.chrisryugj/korean-law-mcp

Step 0: Get an API key (free, 1 minute)

Get a 법제처 Open API key (OC) first. Local installs need it; options that use the hosted server also work without one on a shared quota. Go to the 법제처 Open API page → sign up and log in → "Open API 사용 신청" (apply) → fill in the form and you get a key (e.g. honggildong). Use that key in the configs below.

Option 1: Claude Code plugin (easiest)

If you use Claude Code, two lines are enough. The plugin asks for your API key during install and stores it as sensitive data; leave it empty to use the shared quota.

/plugin marketplace add chrisryugj/korean-law-mcp
/plugin install korean-law@korean-law-marketplace

Then just ask in natural language ("근로기준법 제74조 알려줘", "민법 제750조 판례 검증해줘") and the korean-law MCP tools are called automatically. Update to a new version with:

/plugin marketplace update korean-law-marketplace

The plugin connects to the hosted server https://mcp.gomdori.app/law (nothing is installed on your machine) and sends your key in the apikey header. To avoid the hosted server, use the local install below.

Troubleshooting: Permission denied (publickey)

If install fails with git@github.com: Permission denied (publickey)., the installer tried to clone over SSH and you have no SSH key registered (common for first-time Git users). Either:

1. Force HTTPS (simplest, recommended): run this, then retry /plugin install. It is safe to leave in place afterwards (HTTPS clone always works)

   git config --global url."https://github.com/".insteadOf "git@github.com:"

2. Create and register an SSH key: if you plan to use SSH regularly

   ssh-keygen -t ed25519 -C "your-email@example.com"   # press Enter 3 times
   cat ~/.ssh/id_ed25519.pub                            # copy the output

   Paste the public key into GitHub → Settings → SSH and GPG keys → New SSH key

Option 2: Claude.ai on the web (no install)

Requires a Claude Pro/Max/Team/Enterprise plan (Free allows only one connector).

1. Log in to claude.ai → your name at the bottom of the sidebar → Settings → Connectors

2. Add custom connector → name korean-law (anything works), URL below (replace honggildong with your own key from Step 0)

   https://mcp.gomdori.app/law?oc=honggildong
   

3. Add → open the connector's Configure and set every tool to Always allow (important: no approval prompt each time)

4. Ask "근로기준법 제74조 알려줘" in a chat

To change the connector URL, delete it and add it again. No profile selection needed (10 tools cover all 42 APIs); an existing ?profile=lite&oc=... URL keeps working.

Option 3: Desktop apps (remote server, no install)

Claude Desktop does not support remote HTTP MCP servers directly. Use the mcp-remote adapter (requires Node.js 18+ for npx):

{
  "mcpServers": {
    "korean-law": {
      "command": "npx",
      "args": [
        "-y",
        "mcp-remote",
        "https://mcp.gomdori.app/law?oc=your-api-key"
      ]
    }
  }
}

Cursor, Windsurf, and other clients with native remote HTTP support — use the URL directly:

{
  "mcpServers": {
    "korean-law": {
      "url": "https://mcp.gomdori.app/law?oc=your-api-key"
    }
  }
}

If other MCP servers are already configured, add only the "korean-law": { ... } entry inside "mcpServers". Restart the app after saving.

Option 4: Local install

Requires Node.js 20.19+ (22.12+ recommended).

Auto setup (recommended):

npx --ignore-scripts --omit=optional korean-law-mcp setup

Interactive wizard handles API key input, client selection, and config file registration.
Supports Claude Desktop, Claude Code, Cursor, VS Code, Windsurf, Gemini CLI, Zed, and Antigravity.
Project-folder configs (Claude Code .mcp.json, VS Code .vscode/mcp.json) may be committed to git, so the key is not written in plain text:
Claude Code gets a ${LAW_OC} reference (add export LAW_OC=your-key to your shell profile), and VS Code prompts for the key on first run.

Manual setup:

npm install --ignore-scripts --omit=optional -g korean-law-mcp

Add to your MCP client config, then restart the app:

{
  "mcpServers": {
    "korean-law": {
      "command": "korean-law-mcp",
      "env": {
        "LAW_OC": "your-api-key"
      }
    }
  }
}

Option 5: CLI

npm install --ignore-scripts --omit=optional -g korean-law-mcp
export LAW_OC=your-api-key               # Mac/Linux
set LAW_OC=your-api-key                  # Windows CMD
$env:LAW_OC="your-api-key"              # Windows PowerShell

korean-law "민법 제1조"                  # natural-language query
korean-law search_law --query "관세법"
korean-law get_law_text --mst 160001 --jo "제38조"
korean-law search_precedents --query "부당해고"
korean-law list                          # all tools
korean-law list --category 판례          # filter by category
korean-law help search_law               # tool help

Option 6: Docker

docker build -t korean-law-mcp .
docker run -e LAW_OC=your-api-key -e MCP_HTTP_HOST=0.0.0.0 \
  -e MCP_AUTH_TOKEN=replace-with-a-secret -p 3000:3000 korean-law-mcp

API key delivery (priority order)

Without a key, the public server (mcp.gomdori.app/law) falls back to a shared server key under a limit shared by all keyless users. Sending your own key bypasses that limit (free signup: https://open.law.go.kr).

법제처 API protocol

Calls to the 법제처 API use HTTPS by default. On internal or air-gapped networks where certificate validation is hard, set LAW_API_PROTOCOL=http. Allowed values are http and https; anything else (or unset) means https. Putting it in the client config's env block is clearest:

{
  "mcpServers": {
    "korean-law": {
      "command": "korean-law-mcp",
      "env": {
        "LAW_OC": "your-api-key",
        "LAW_API_PROTOCOL": "http"
      }
    }
  }
}

A shell variable or a .env file (LAW_OC=... plus LAW_API_PROTOCOL=http) also works:

export LAW_API_PROTOCOL=http        # Mac/Linux
set LAW_API_PROTOCOL=http           # Windows CMD
$env:LAW_API_PROTOCOL="http"       # Windows PowerShell

National Tax Service precedent server: TLS / proxy

When a National Tax Service precedent body is missing from the 법제처 JSON response, and always for National Tax Service interpretation (nts) bodies, the server queries taxlaw.nts.go.kr. That server redirects HTTP to HTTPS, so regardless of LAW_API_PROTOCOL=http the Node.js runtime must trust the https://taxlaw.nts.go.kr certificate. Behind corporate networks, firewalls or SSL-inspection proxies the page may open in a browser while Node.js fetch() fails with [EXTERNAL_API_ERROR] fetch failed (different certificate store and proxy settings). Check the connection from Node.js first:

node -e "fetch('https://taxlaw.nts.go.kr/qt/USEQTA002P.do?ntstDcmId=200000000000019303').then(r=>console.log(r.status,r.url)).catch(e=>console.error(e.name,e.message,e.cause))"

If you must go through a web proxy, set its address (applies to the external HTTPS connection of the NTS precedent fallback). On Windows, register the system variable from an administrator terminal with setx, then restart Windows or the Node.js process:

LAW_EXTERNAL_HTTPS_PROXY=http://proxy-host:8080

setx LAW_EXTERNAL_HTTPS_PROXY http://proxy-host:8080 /M

If certificate validation still fails through the proxy, you can temporarily disable TLS verification for this project's external HTTPS proxy path only, for diagnosis. Never leave it on in production; the second line removes it after diagnosis:

setx LAW_EXTERNAL_TLS_REJECT_UNAUTHORIZED 0 /M
reg delete "HKLM\SYSTEM\CurrentControlSet\Control\Session Manager\Environment" /v LAW_EXTERNAL_TLS_REJECT_UNAUTHORIZED /f

Usage Examples

Basic lookups

User: "관세법 제38조 알려줘"
→ search_law("관세법") → get_law_text(mst, jo="003800")

User: "화관법 최근 개정 비교"
→ "화관법" → "화학물질관리법" auto-resolved → compare_old_new(mst)

User: "근로기준법 제74조 해석례"
→ search_interpretations("근로기준법 제74조") → get_interpretation_text(id)

User: "산업안전보건법 별표1 내용"
→ get_annexes("산업안전보건법 별표1") → HWPX download → Markdown table

Abbreviations are expanded even when combined with other words: 화관법 시행령 → 화학물질관리법 시행령, 중처법 제4조 책임자 → 중대재해 처벌 등에 관한 법률 제4조 책임자.

Natural-language scenarios

Ask in natural language and the matching extra analysis is added automatically. Scenarios are detected from query keywords or set explicitly with the scenario parameter.

Every result ends with suggested follow-up queries.

Verification and analysis

Actual verify_citations output:

"Civil Act Art. 750 … Labor Standards Act Art. 60(1) … Commercial Act Art. 401-2(7) … Criminal Act Art. 9999"

✓ Civil Act Article 750 (Tort liability) — exists
✓ Labor Standards Act Article 60 (Annual paid leave) Paragraph 1 — exists
✗ Commercial Act Article 401-2 — Paragraph 7 doesn't exist (max Paragraph 2)
✗ Criminal Act Article 9999 — no such article (valid range: Art.1~Art.372)

Handy options

Tool Structure (10 tools)

10 tools are advertised. The former 8 chain_* tools are task values of legal_research, and the 4 analysis features are mode values of legal_analysis. Other specialized tools stay reachable via discover_tools → execute_tool, and calling the old tool names directly still works.

legal_research tasks (formerly chain_*)

legal_analysis modes

Full tool reference: docs/API.md.

Features

• 42 APIs → 10 Tools — Statutes, precedents, admin rules, ordinances, constitutional decisions, tax rulings, customs interpretations, treaties, institutional rules, legal terminology
• MCP + CLI — Use from Claude Desktop or from your terminal
• Korean Law Intelligence — Auto-resolves abbreviations (화관법 → 화학물질관리법), converts article numbers (제38조 ↔ 003800), visualizes 3-tier delegation
• Currency checks — [현행] / ⚠️[연혁-과거버전] labels in search results, pending amendments and renames shown alongside, repealed statutes point to the repeal reason and successor regulation
• Point-in-time across renames — versions are chained by statute ID, so lookups reach the years before a law was renamed
• Failures are never reported as "not found" — lookup failures, maintenance pages and exhausted budgets carry explicit markers such as [NOT_FOUND]
• Annex Extraction — Downloads HWPX/HWP/PDF/XLSX/DOCX annexes and converts to Markdown (kordoc engine)
• 8 chains + 9 scenarios — Situation-specific analysis added automatically (penalty reduction, customs clearance, delegated legislation, etc.)
• 21 Decision Domains — search_decisions covers precedents, constitutional court, tax tribunal, FTC, NLRC and more in one tool
• Caching — 1-hour search cache, 24-hour article cache
• Remote Endpoint — Use without installation via https://mcp.gomdori.app/law (the legacy korean-law-mcp.fly.dev/mcp stays backward compatible)

Environment Variables

All numeric limits are validated as whole numbers during startup. Invalid values fail startup rather than weakening a limit. legal_research and other documented chain tools share the 48-attempt request budget; JSON-RPC batch siblings share accounting but retain independent MCP cancellation signals. get_batch_articles is capped at 20 statutes and 100 articles in total; HTTP disconnects and MCP cancellations propagate through fetches, retry waits and body reads.

HTTP deployment defaults

HTTP mode is local by default: it binds only to 127.0.0.1, does not trust X-Forwarded-For, and leaves token authentication optional for that loopback-only use. For a reverse-proxy deployment, set both the explicit public bind and the exact trusted hop count, for example:

MCP_HTTP_HOST=0.0.0.0 TRUST_PROXY=1 MCP_AUTH_TOKEN=replace-with-a-secret \
  korean-law-mcp --mode http --port 8000

MCP_ALLOW_UNAUTHENTICATED_REMOTE=1 preserves intentionally public legacy deployments, but emits a startup warning and should only be used where another access boundary is in place.

Dependency and install boundary

kordoc remains because annex parsing is a reachable server feature. Its known-good pure-JS pdfjs-dist@4.10.38 runtime is pinned as a normal dependency; optional OCR/ML/native helpers are not needed by this server. Documented and Docker installs use --omit=optional --ignore-scripts. CI and publishing retain optional development-tool bindings with scripts disabled during validation, then prune to the production graph and run the PDF annex smoke test. Scanner reports for transitive HTTP-framework packages should be evaluated against the reachable server path rather than treated as proof that the server exposes the affected middleware.

Documentation

• docs/API.md — Tool reference
• docs/ARCHITECTURE.md — System design
• docs/DEVELOPMENT.md — Development guide
• CHANGELOG.md — Release history

FAQ

How do I search Korean statutes and court precedents from Claude or ChatGPT?
Connect this MCP server. In Claude.ai, add https://mcp.gomdori.app/law?oc=YOUR_KEY as a custom connector. For Claude Desktop, Cursor, Windsurf and Zed see Quick Start; for ChatGPT see the connection video (Korean narration).

Is it free?
Yes. The code is MIT-licensed, and the 법제처 Open API key it needs is free (open.law.go.kr).

Can it catch legal citations an LLM made up?
legal_analysis(mode="verify_citations") checks the statute articles and case numbers cited in a text against the official 법제처 source, for existence and for content. mode="cite_check" tells whether a precedent is still good law.

What does it cover?
Statutes, precedents, administrative rules, local ordinances, treaties and legal interpretations (including the National Tax Service), plus annexes and forms. It also resolves past versions of a law and points repealed statutes to their successors.

Star History

Data sources

Statute, precedent, administrative-rule, ordinance, treaty and interpretation texts come from the 법제처 National Law Information Center OPEN API (https://open.law.go.kr/). National Tax Service interpretations use the NTS legal information system.

For any decision that needs legal force, always check the original text at the National Law Information Center. This tool may process and summarize what it retrieves.

Each user must obtain their own API key (LAW_OC) from 법제처; a key may be used only by the person it was issued to.

Credits

• 법제처 Open API — Korea's official legal database
• Anthropic — Model Context Protocol
• kordoc — HWP/HWPX parser (same author)

License

MIT

Third-party implementation references and data-source notices: see NOTICE.

_{Made by a Korean civil servant @ 광진구청 AI동호회 AI.Do}