tpt-law

Law as executable, auditable, AI-consumable infrastructure.

Open source (MIT). New Zealand as the first jurisdiction. Built to scale to any legal system.

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Vision

Legal systems are slow, expensive, and inconsistent — not because the law is unclear, but because applying it requires enormous human effort for tasks that are fundamentally mechanical. tpt-law encodes legislation as formal, executable rules so that AI systems can apply the law correctly, consistently, and with a full audit trail.

The long-term goal is AI-assisted legal judgment: starting with decision-support tools, building toward systems that can autonomously apply law to facts in bounded domains.

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Architecture

┌─────────────────────────────────────┐
│  AI / Applications  (your code)     │
└──────────────┬──────────────────────┘
               │ REST API / MCP tool-use
┌──────────────▼──────────────────────┐
│  tpt-law engine  (this repo)        │
│  POST /apply  ·  GET /rules         │
└──────────────┬──────────────────────┘
               │ loads
┌──────────────▼──────────────────────┐
│  Rule library  (this repo)          │
│  rules/nz/income-tax-act-2007/      │
│  rules/nz/social-security-act/      │
└─────────────────────────────────────┘

The rule library is the public good — open, auditable, correctable by anyone.
The engine is the infrastructure — jurisdiction-agnostic, runs any rule library.
AI is the application layer — queries the engine via standard HTTP or MCP.

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Quickstart

cd engine
npm install
npm run dev

Apply Working for Families rules to a set of facts:

curl -X POST http://localhost:3000/apply \
  -H "Content-Type: application/json" \
  -d '{
    "jurisdiction": "nz",
    "legislation": "income-tax-act-2007",
    "facts": {
      "dependent_children": 2,
      "nz_tax_resident": true,
      "is_principal_caregiver": true,
      "is_transitional_resident": false,
      "annual_income": 60000,
      "receiving_main_benefit": false,
      "hours_worked_per_week": 40
    },
    "as_at": "2024-01-01"
  }'

Response:

{
  "jurisdiction": "nz",
  "legislation": "income-tax-act-2007",
  "as_at": "2024-01-01",
  "satisfied_rules": ["wff_eligible", "wff_ftc_amount", "wff_iwtc_eligible", "wff_iwtc_amount"],
  "decision": {
    "wff_eligible": true,
    "ftc_annual": 7384,
    "iwtc_eligible": true,
    "iwtc_annual": 3770
  },
  "trace": [
    {
      "rule": "wff_eligible",
      "source": "Income Tax Act 2007 s.MD.1",
      "status": "satisfied",
      "conditions": [
        { "outcome": "matched", "fact": "dependent_children", "description": "dependent_children (2) >= 1" },
        { "outcome": "matched", "fact": "nz_tax_resident", "description": "nz_tax_resident = true" },
        { "outcome": "matched", "fact": "is_principal_caregiver", "description": "is_principal_caregiver = true" }
      ],
      "result": { "wff_eligible": true }
    }
  ],
  "missing_facts": []
}

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Rule Format

Rules are YAML files in rules/:jurisdiction/:act/. Each rule is immutable once published — new law versions get new files with an effective_from date.

rule: wff_eligible
source: "Income Tax Act 2007 s.MD.1"
effective_from: "2007-04-01"
given:
  - fact: dependent_children
    greater_than_or_equal: 1
  - fact: nz_tax_resident
    equals: true
  - fact: is_principal_caregiver
    equals: true
unless:
  - fact: is_transitional_resident
    equals: true
result:
  wff_eligible: true

See docs/rule-format.md for the full specification.

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Project Structure

tpt-law/
├── engine/          # TypeScript execution engine + REST API
│   └── src/
│       ├── loader/  # Rule file loading and validation
│       ├── engine/  # Rule evaluation logic
│       ├── api/     # Fastify HTTP routes
│       └── types/   # Shared TypeScript types
├── rules/
│   └── nz/          # New Zealand legislation (first jurisdiction)
├── schemas/         # JSON Schema for rule format validation
├── docs/            # Encoding guides, API reference
└── examples/        # Integration examples (Claude, OpenAI, MCP)

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Principles

• Auditability first — every decision includes a full reasoning trace
• Temporal correctness — as_at date selects the right law version for any point in time
• Open rule library — the encoded law is the public good; anyone can propose corrections
• Jurisdiction-agnostic engine — NZ is the first model, not a constraint
• AI-native API — designed for tool-use and MCP from the ground up

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Contributing

See CONTRIBUTING.md for how to encode a new law or propose a correction to existing rules.

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Status

Active development. Phases 1–10 complete. Phase 11 (Top 20 NZ Statutes) is at 25% coverage — 5 of 20 priority acts encoded. See TODO.md for the full roadmap.

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License

MIT — see LICENSE.