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NEXUS LEGAL × MCP

Your Claude now speaks the law of 60 jurisdictions.

Official Nexus Legal MCP server. Connect in 2 minutes and start invoking ISO 31000 analysis, cross-audit, brief drafting, Monte Carlo simulation, multi-jurisdictional doctrine search, case-law search across 60 jurisdictions, adversarial red team, multi-LLM second opinion and cross-border comparison — all from your Claude chat.

Get my MCP key →How it works ↓
Claude Desktop · Claude Code · Cursor · Cline · ZedGDPR Compliant · Zero Retention · EU-hostedPay per use · no annual subscriptionOpen source (MIT)

AVAILABLE IN CLAUDE

Add Nexus Legal directly in Claude.

Nexus Legal now runs as a remote connector you can add today in claude.ai (web and desktop) — no install, no npm, no config file. Sign in once with OAuth and Claude can invoke the read-only legal tools: deterministic citation-fidelity verification (verify_cita), jurisprudence search, legal analysis and more across 60 jurisdictions, with Zero-Retention (EU-hosted, no document persistence). Available now as a custom connector — directory listing under review.

Connector URL

↳https://legal.nexusquantum.legal/api/mcp
01

Open Connectors in Claude

In Claude (claude.ai or desktop), go to Settings → Connectors → 'Add custom connector'.

02

Paste the URL

Paste https://legal.nexusquantum.legal/api/mcp and continue.

03

Authorize with OAuth

Authorize via OAuth 2.0. The Nexus legal tools then appear in your chat, ready to invoke.

WHAT IS MCP

One interface. Twenty-seven legal capabilities.

What is the Model Context Protocol?

MCP is the open standard, published by Anthropic in 2024, that lets an AI client (like Claude Desktop) discover and use external tools with user permission. Think of it as plugins for AI assistants: the client remains Claude; the tools can come from specialised third parties. Nexus Legal exposes its 27 legal capabilities as an MCP server — meaning any lawyer already using Claude Desktop, Claude Code or Cursor can start requesting specialised legal analysis from their regular chat, without opening a browser, without copy-pasting a contract twice, without switching apps.

Before: Claude thinks in general, Nexus thinks in law. You had to switch between them for each contract.

Now: you talk to Claude. When your query requires jurisdictional rigour, Claude offers to invoke Nexus automatically. Nexus responds with auditable certainty locks [L1]–[L5] and a citation-anchored audit trail you can present for review across 60 covered jurisdictions. Claude integrates the answer into the conversation.

27 LEGAL CAPABILITIES

What you can ask Claude to do

Each tool is invoked by Claude when the query matches — or you can call them explicitly.

verify_cita

Citation Verification

The citation-fidelity verification core. Checks every legal citation against the source corpus before you rely on it — flagging citations that are paraphrased, altered or not found, each marked with a verification seal ([L4-N] statute / [L2-J] case-law).

Balance (+ case-law add-on for case citations)

nexus_analyze

Primary ISO 31000 Analysis

Full analysis of contracts, briefs, rulings and orders with certainty locks [L1]–[L5] and a NEXUS-AUDIT-TRAIL block.

1-3 credits

nexus_consulta

Legal Query

Natural-language question with or without a context document. Supports multi-turn conversational threads.

1 credit

nexus_draft

Brief Drafting

Generates a first draft of an appeal, complaint, reply, clause or opinion following the MODULE-DRAFT format.

2-4 credits

nexus_audit

Node B Cross-Audit

Re-examines a Node A analysis against the source document. Detects unsupported claims, mis-assigned locks, omissions and contradictions.

1-2 credits

nexus_monte_carlo

Scenario Simulation

Stress-tests the risk profile under defined variables. Calculates a Contractual Resilience Index 0–100. Ideal for M&A and due diligence.

4 credits

nexus_doctrina

Multi-Jurisdiction Regulatory Doctrine

Searches the curated corpus of binding regulatory rulings, tax authority resolutions, council of state opinions and equivalent criteria across supported jurisdictions. For fiscal and regulatory questions.

1 credit

nexus_opinion

Multi-LLM Second Opinion

Takes a Node A response and re-examines it with a different LLM looking for omissions, biases and errors. For high-stakes cases.

2 credits

nexus_redteam

Adversarial Red Team

Hostile analysis as opposing counsel: legal gaps, trap clauses, catastrophic risks. Structured JSON output.

5 credits

nexus_adversarial

Adversarial Argumentation

For each conclusion of analysis A, builds the strongest argument the opposing party would raise. To prepare for litigation.

2-3 credits

nexus_cross_border_compare

Multi-Jurisdiction Comparison

Compares how each legal system (2–15 countries) treats the given facts or contract. For clients operating across borders.

2-4 credits

nexus_jurisprudencia_search

Jurisprudence Search

Vector search across the curated multi-jurisdiction corpus covering 60 jurisdictions. Locate case law on a specific topic.

Balance + case-law add-on

cruce_normativa_jurisprudencia

Statute ↔ Case-law Cross-reference

Cross-references a statute article with the case law that applies it — and any ruling with the articles it cites — across the curated corpus.

Balance + case-law add-on

plazos_calcular

Procedural Deadline Calculator

Calculates procedural and limitation deadlines, accounting for business days, official holidays and tolling rules. Covers Spain and England & Wales only: Scotland and Northern Ireland are refused on purpose, because their rules and their court holidays differ. Always confirm against the official court calendar.

Requires balance

nexus_consensus

Multi-Agent Consensus

Runs Node A and Node B against each other in a loop until they converge or the disagreement is put on the record. A long operation by design: it takes three to six minutes.

3-7 credits

nexus_playbook

Negotiation Playbook

Strategic playbook for a negotiation: positions, trade space, fallbacks and the arguments the other side is most likely to make.

2-3 credits

nexus_compare_versions

Version Comparison

Compares two versions of the same document and reports what changed in substance, not only in wording.

2 credits

nexus_conflict_check

Conflict Check

Checks the parties on a matter against the firm's existing engagements for conflicts of interest.

1 credit

nexus_chat

Case-File Chat

Legal chat that carries the context of an open matter, so you are not re-explaining the file on every question.

1 credit

box_analyze

Box File Analysis

Analyses a document held in Box by its file id. Requires an active Box connection. Box is the only document manager exposed through MCP today.

1-2 credits

nexus_normativa_search

Legislation Search

Semantic search across legislation in force, by jurisdiction.

Balance + legislation add-on

nexus_normativa_articulo

Provision at a Date

Returns the literal text of a provision as it stood on a given date, which is not the same thing as the consolidated text published today.

Balance + legislation add-on

nexus_normativa_pyramid

Normative Hierarchy

Coverage by level of the hierarchy of norms, so you can see where the corpus is thin before you rely on it.

Requires balance

nexus_verificacion

Verification Centre

Checks every citation in a document at once rather than one at a time. Deterministic: no model sits in the path, so there is no LLM cost.

Requires balance

nexus_inbox

Firm Inbox

The firm's attention queue: what is waiting, on which matter, and since when.

Requires balance

nexus_corpus_coverage

Case-Law Corpus Inventory

What the case-law corpus actually holds, jurisdiction by jurisdiction. Read-only.

No cost

nexus_normativa_coverage

Legislation Coverage

Which jurisdictions are covered for legislation and how fresh each one is. Read-only.

No cost

Credit ranges are per call and depend on document length and depth. Nothing here is free of charge; the two read-only inventories consume no credits.

WHY NEXUS MCP

Built for jurisdictions Claude doesn't know

Beyond Claude alone

Claude Pro/Teams excels at general legal reasoning. But it has no curated jurisdictional corpus and no auditable certainty locks with a citation-anchored audit trail. Nexus adds exactly that: 60 jurisdiction modules + curated corpus + cryptographically sealed audit trail + Node B cross-audit.

60 jurisdictions vs. 12 English-only plugins

The 12 plugins Anthropic announced for 'Claude for Legal' are US-centric: US Litigation, US Corporate, US Privacy. Nexus covers hand-curated modules across 59 countries plus the European Union as a supranational layer — spanning Latin America, Europe, Asia-Pacific and Africa. The only serious option if you litigate or advise across borders.

Pay per use. No annual commitment.

Comparable suites charge €10–50k per year. Nexus is pay-per-use, installed in 2 minutes, no annual commitment. For a firm not ready to commit long-term, Nexus is the ideal on-ramp: try it, scale it, decide.

EU soil. Zero Retention by default.

We process in RAM in the Netherlands (Railway europe-west4) and do NOT persist documents to a database. For public-sector or sensitive clients, being able to certify Zero Retention on EU soil is a blocking requirement. Nexus can prove no sensitive data ever leaves EU jurisdiction.

GET STARTED

Connected in 3 steps. 2 minutes.

01

Generate your MCP key (30 sec)

Go to nexusquantum.legal/developers, click '+ Create key', choose 'MCP Server', name it and click Create. Copy the nlk_... key. Shown only once.

02

Paste the config in your client (60 sec)

Add the block below to your client config file. Claude Desktop (Mac): ~/Library/Application Support/Claude/claude_desktop_config.json · Windows: %APPDATA%\Claude\claude_desktop_config.json · Claude Code: run claude mcp add nexus-legal -- npx -y @nexus-legal/mcp

03

Restart and start asking (30 sec)

Claude Desktop shows a 🔌 icon with 27 Nexus tools available. Try: 'Analyse this contract with Nexus, ES jurisdiction, conservative profile.' or 'Search TS case law on unfair floor clauses.'

claude_desktop_config.json
{
  "mcpServers": {
    "nexus-legal": {
      "command": "npx",
      "args": ["-y", "@nexus-legal/mcp"],
      "env": {
        "NEXUS_API_KEY": "nlk_TU_CLAVE_AQUI"
      }
    }
  }
}

USE CASES

How lawyers use it every day

S
Sarah
General practice lawyer

Receives a 40-page distribution contract at 6:30 pm for signature tomorrow. Before: opens Nexus web, uploads PDF, waits for analysis, downloads it, opens in Word, annotates. 25 minutes.

Now: drags the PDF to Claude Desktop, types 'analyse with Nexus, ES, conservative profile'. 2 minutes later she has the full report in chat with [L5-C] locks on the 3 critical clauses. Done in 8 minutes.

J
James
M&A associate

Preparing a bilateral SPA Spain–Mexico. Needs: choice-of-law comparison, CDI verification, red team on indemnification clauses, Monte Carlo simulation. Before: 4 different tools, 4 logins, 4 lost contexts.

Four MCP tools chained from Claude Code, where he was already drafting. One conversation. Done.

FAQ

Frequently asked questions

Nexus is already in your Claude.

Add 27 specialised legal capabilities to your existing workflow. No annual contract, no new interface to learn.

Get started →Generate MCP key

@nexus-legal/mcp · MIT · github ↗