Lex

UK legal API for AI agents and researchers. Access comprehensive UK legislation data with semantic search and Model Context Protocol integration.

Python 3.12+ License

What is Lex?

Lex provides programmatic access to 8.4M+ UK legal documents - legislation, amendments, and explanatory notes - with hybrid semantic search.

This is an experimental service and should not be used as a production dependency.

Dataset Coverage

• Legislation - 220K Acts and Statutory Instruments (1267-present, complete from 1963)
• Amendments - 892K legislative changes and modifications
• Explanatory Notes - 89K notes providing legislative context
• Case Law - 70K judgments and 4.7M paragraphs (temporarily disabled pending TNA licence)
• PDF Digitisation - Historical legislation (pre-1963) digitised using AI

What Can You Build?

• Legal Research - Find relevant legislation in seconds
• Policy Analysis - Track legislative changes over time
• AI Grounding - Ground AI assistants in authoritative UK legal sources

MCP Integration

Connect AI assistants to Lex via Model Context Protocol. See the live documentation for setup instructions for:

• Claude Desktop
• Claude Code
• Cursor
• Microsoft Copilot Studio
• VS Code + GitHub Copilot

Local Development

Prerequisites

• Python 3.12+
• uv
• Docker & Docker Compose
• Azure OpenAI credentials

Quick Start

# Clone and setup
git clone https://github.com/i-dot-ai/lex.git && cd lex
cp .env.example .env  # Add your Azure OpenAI keys

# Start services and load sample data
docker compose up -d
make ingest-all-sample

# Visit http://localhost:8000/docs for API documentation

Data Loading

# Quick samples (recommended for testing)
make ingest-legislation-sample
make ingest-all-sample

# Full datasets (production use)
make ingest-legislation-full
make ingest-all-full

# Create indexes for fast filtering
uv run python scripts/create_payload_indexes.py

Development Commands

make install          # Install dependencies
make test             # Run tests
make run              # Start API locally (without Docker)
uv run ruff format .  # Format code

Architecture

lex/
├── src/
│   ├── lex/              # Data pipeline (scraping, parsing, indexing)
│   └── backend/          # API server (FastAPI + MCP)
├── infrastructure/       # Azure Bicep templates and deploy scripts
├── scripts/              # Maintenance, migration, and export utilities
├── tests/                # Test suite
└── docs/                 # Documentation

Documentation

• System Architecture - Start here for the full picture
• Deployment Guide
• Operations Runbook
• Data Pipeline Guide
• API Reference
• Troubleshooting
• Contributing

Acknowledgements

Built with support from The National Archives and Ministry of Justice.

License

MIT - See LICENSE for details.