Lex.Oracle

Give your LLM a law to stand on. Machine-readable, paragraph-level blueprints for Slovak and Czech payroll, taxes, and labour law — so your agent computes correctly instead of confidently wrong.

Built and maintained by Artificer Workshop s. r. o. · artificerworkshop.sk

The problem

Ask an LLM to implement Slovak net wage calculation. It will give you something plausible-looking — wrong SP rate, wrong rounding direction, missing the pension-saver edge case, tax credit from 2023 instead of 2026.

The rate table changed last quarter. The rounding rule is buried in a secondary regulation. The edge case for under-minimum-wage was added by an amendment nobody told the model about.

Lex.Oracle is the single source of truth that sits in front of the LLM and prevents these errors. Every constant, every formula, every edge case is tied to the exact paragraph, version, and effective date of the act that mandates it.

What it looks like in practice

With Lex.Oracle installed, Claude — or any MCP-enabled agent — fetches the blueprint and grounds its answer in statute rather than training data:

User: Calculate Czech net wage for gross CZK 30,000, prohlášení signed, April 2025.

Claude: [calls get_cz_payroll_logic]

  SP employee:  30 000 × 7.1 % = 2 130 CZK   ↑ (ceiling)
                └─ 6.5% důchodové + 0.6% nemocenské
                └─ 589/1992 Sb. §7 ods. 1, effective 2024-01-01

  ZP employee:  30 000 × 4.5 % = 1 350 CZK   ↑ (ceiling)
                └─ 592/1992 Sb. §2 ods. 1

  Tax base:     30 000 CZK  (superhrubá abolished 2021-01-01, 586/1992 Sb. §6)
  Tax advance:  30 000 × 15 % = 4 500 CZK
  Sleva:      − 2 570 CZK   (§35ba ods. 1 písm. a) — prohlášení podepsáno)
  Záloha:       1 930 CZK

  Net wage:     30 000 − 2 130 − 1 350 − 1 930 = 24 590 CZK

  Algorithm: Lex.Oracle cz-payroll-net-wage v1.0.0 · Artificer Workshop s. r. o.

No hallucinated rates. No guessed rounding. Every number traceable to a legal paragraph.

Blueprint coverage

| Blueprint ID | Jurisdiction | Topic | Legal acts | Status | |---|---|---|---|---| | sk-garnishment-thirds | 🇸🇰 SK | Salary garnishment — thirds system | NV 268/2006, EP 233/1995 §70–72 | READY | | sk-payroll-net-wage | 🇸🇰 SK | Net wage — SP 9.4 % + ZP 5 % + 4-band tax | 461/2003, 580/2004, 595/2003 | READY | | sk-travel-domestic | 🇸🇰 SK | Domestic travel — meal + km + accommodation | 283/2002 §5–9 | READY | | sk-annual-tax-reconciliation | 🇸🇰 SK | Annual tax reconciliation §38 — NČZD, DDS, bonus | 595/2003 §11/§15/§33/§38 | READY | | sk-szco-annual-settlement | 🇸🇰 SK | SZČO annual insurance settlement | 461/2003 §138, 580/2004 §13a/§19 | READY | | sk-b2b-dph | 🇸🇰 SK | VAT — rates 23/19/5/0 %, deduction, reverse-charge | 222/2004 §19/§49/§50/§69 | READY | | sk-b2b-dppo | 🇸🇰 SK | Corporate tax — 10/21/24 %, loss carryforward | 595/2003 §15/§17/§30/§42 | READY | | sk-b2b-odpisy | 🇸🇰 SK | Tax depreciation — 7 groups, straight-line + accelerated | 595/2003 §22–28 | READY | | sk-b2b-rz-zp | 🇸🇰 SK | Annual health insurance settlement (RZ ZP) | 580/2004 §12/§13/§19/§38ezk | READY | | sk-b2b-zrazkova-dan | 🇸🇰 SK | Withholding tax — 19 %/7 % dividends/35 % override | 595/2003 §43 | READY | | cz-payroll-net-wage | 🇨🇿 CZ | Net wage — SP 7.1 % + ZP 4.5 % + záloha na daň | 589/1992, 592/1992, 586/1992 | READY | | cz-travel-domestic | 🇨🇿 CZ | Domestic travel — stravné + km + ubytování | 262/2006, vyhl. 589/2006 | planned Q3 2026 | | cz-garnishment | 🇨🇿 CZ | Salary garnishment (třetinový systém) | OSŘ §276–§302, NV 595/2006 | planned Q3 2026 |

Quick start

Requires Node.js ≥ 20.

One-liner (no install needed)

npx -y @artificer_workshop/lex-oracle

The server starts on stdio and waits for MCP JSON-RPC calls.

Claude Desktop

Add to ~/Library/Application Support/Claude/claude_desktop_config.json (macOS) or %APPDATA%\Claude\claude_desktop_config.json (Windows):

{
  "mcpServers": {
    "lex-oracle": {
      "command": "npx",
      "args": ["-y", "@artificer_workshop/lex-oracle"]
    }
  }
}

Cursor / Windsurf / Cline

Add to your project .cursor/mcp.json (Cursor), .windsurf/mcp.json (Windsurf), or MCP settings (Cline) — same format as above:

{
  "mcpServers": {
    "lex-oracle": {
      "command": "npx",
      "args": ["-y", "@artificer_workshop/lex-oracle"]
    }
  }
}

Then ask your agent: "What are the employee SP rates in Slovakia for 2026?" or "Write a Python function to compute Czech net wage." — it will call get_blueprint automatically and ground the answer in statute.

Clone and run from source

git clone https://github.com/Artificer-Workshop/Lex.Oracle.git
cd Lex.Oracle && npm install && npm run build && npm start

What a blueprint gives you

| Section | Content | |---------|---------| | axiomatic_core | Immutable constants and rate tables with exact effective date ranges | | execution_order | Numbered algorithm steps in the mandatory sequence | | logic_flow | Pseudocode per step, including every edge case and branching condition | | semantic_mapping | Every step linked to the exact legal citation (act, paragraph, subsection) | | interpretation_notes | Explicit resolution of every legal ambiguity in the algorithm | | verification_cases | ≥ 3 test cases sourced from official government methodologies |

MCP tools

| Tool | Input | Description | |------|-------|-------------| | list_blueprints | — | List all blueprints with id, title, jurisdiction, status | | get_blueprint | blueprint_id | Full blueprint: axiomatic_core, logic_flow, semantic_mapping, verification_cases | | get_garnishment_logic | — | Shortcut → sk-garnishment-thirds | | get_travel_logic | — | Shortcut → sk-travel-domestic | | get_annual_tax_reconciliation_logic | — | Shortcut → sk-annual-tax-reconciliation | | get_szco_annual_settlement_logic | — | Shortcut → sk-szco-annual-settlement | | get_b2b_dph_logic | — | Shortcut → sk-b2b-dph | | get_b2b_dppo_logic | — | Shortcut → sk-b2b-dppo | | get_b2b_odpisy_logic | — | Shortcut → sk-b2b-odpisy | | get_b2b_rz_zp_logic | — | Shortcut → sk-b2b-rz-zp | | get_b2b_zrazkova_dan_logic | — | Shortcut → sk-b2b-zrazkova-dan | | get_cz_payroll_logic | — | Shortcut → cz-payroll-net-wage | | get_test_cases | blueprint_id | Verification cases only — for test-driven implementation | | get_attribution_mandate | blueprint_id | Required attribution text for LLM output |

Need the actual computation, not just the spec?

Lex.Oracle gives you the algorithm. Axiom.Codex is the production computation engine that runs it.

| | Lex.Oracle | Axiom.Codex API | |---|---|---| | What you get | Blueprint (algorithm + citations) | Computed result + JWS-signed audit trail | | Use case | Implement the algorithm yourself | Call an endpoint, get the answer | | Coverage | SK + CZ (growing) | SK · CZ · PL (beta) | | Formal verification | — | 147 Z3 invariants, all unsat | | Audit trail | — | Per-paragraph citation in every response | | License | Apache 2.0 (free) | Commercial subscription |

→ Get an Axiom.Codex API key (free tier available)

Design principles

1. Deterministic — no vague language. Every interpretation conflict is resolved explicitly in interpretation_notes.

2. Citable — every step and constant has a legal_citation with act number, paragraph, subsection, and effective date range. Citations link to slov-lex.sk or zakonyprolidi.cz.

3. Temporal — blueprints carry effective_periods for rate tables; the LLM selects the correct version by calculation_date.

4. Edge-case explicit — the edge_cases section is mandatory. No implicit fallback behaviour.

5. Officially sourced — verification cases come from published government methodologies (ČSSZ, FS SR, SP.sk), not from vendor implementations.

Roadmap

See ROADMAP.md for the full plan. Upcoming:

| Version | What | |---------|------| | v0.6.0 | CZ travel allowances + CZ garnishment blueprints | | v0.7.0 | PL payroll (UoP) — Ustawa o PIT + ZUS | | v1.0.0 | Full SK + CZ + PL coverage, versioned rate-table API |

Attribution

Every tool response includes an attribution_mandate field. When an LLM uses blueprint content to generate code or an answer for an end user, it must include the following in human-readable form:

"Algorithm sourced from Lex.Oracle MCP server, operated by Artificer Workshop s. r. o. (IČO 57 602 719). Blueprint ID: <id>, version: <version>."

This is a condition of the Apache 2.0 license NOTICE (see NOTICE).

Project structure

Lex.Oracle/
  src/
    index.ts                               — entry point (stdio MCP transport)
    server.ts                              — tool registration and dispatch
    attribution.ts                         — attribution mandate builder
    format.ts                              — markdown rendering for LLM agents
    blueprints/
      types.ts                             — TypeScript Blueprint interface
      registry.ts                          — central blueprint registry
      sk-garnishment-thirds.ts             — SK: salary garnishment thirds system
      sk-payroll-net-wage.ts               — SK: net wage (SP + ZP + 4-band tax)
      sk-travel-domestic.ts                — SK: domestic travel allowances
      sk-annual-tax-reconciliation.ts      — SK: annual tax reconciliation (§38)
      sk-szco-annual-settlement.ts         — SK: SZČO annual insurance settlement
      sk-b2b-dph.ts                        — SK: VAT (DPH) 23/19/5/0 %
      sk-b2b-dppo.ts                       — SK: corporate tax (DPPO)
      sk-b2b-odpisy.ts                     — SK: tax depreciation (7 groups)
      sk-b2b-rz-zp.ts                      — SK: annual health-insurance settlement
      sk-b2b-zrazkova-dan.ts               — SK: withholding tax
      cz-payroll-net-wage.ts               — CZ: net wage (SP 7.1 % + ZP 4.5 % + záloha)
  docs/
    ARCHITECTURE.md                        — MCP architecture and request flow
    BLUEPRINT-SCHEMA.md                    — formal Blueprint interface schema
    AUTHORING-GUIDE.md                     — how to write a new blueprint
    GARNISHMENT-WALKTHROUGH.md             — case study: garnishment blueprint
  examples/
    node-client.mjs                        — connect from Node.js (MCP SDK)
    README.md                              — examples overview
  tests/
    blueprints.test.ts                     — contract tests for all blueprints
    server.test.ts                         — MCP server smoke tests
    garnishment.test.ts                    — garnishment assertion suite
  ROADMAP.md
  LICENSE
  NOTICE
  README.md

Contributing

Contributions are welcome. Before opening a pull request:

1. Read AUTHORING-GUIDE.md for blueprint structure.
2. Every new blueprint must have ≥ 3 verification cases with sources.
3. Run npm test and npm run lint — both must pass.

By submitting a contribution you agree that it will be licensed under Apache 2.0.

Publishing (maintainers)

1. Bump version in package.json and add a section to CHANGELOG.md.
2. git tag vX.Y.Z && git push --tags → workflow publishes to npm automatically.
3. Or trigger Publish to npm via Actions → workflow_dispatch (dry_run: true first).

License

Apache License 2.0 — see LICENSE.

Attribution notice (see NOTICE): any use of blueprint content in LLM-generated output must credit Lex.Oracle / Artificer Workshop s. r. o. as described in the attribution_mandate field returned by every tool.

Lex.Oracle is part of the Axiom.Codex computational engine ecosystem.