pii-shield

PII Shield

MCP server + Skill for Claude Desktop (Cowork) that automatically anonymizes documents before Claude sees them — and restores everything back after analysis.

The Problem

You want Claude to review contracts, draft legal memos, compare documents, or suggest edits — but the documents contain real names, addresses, emails, phone numbers, and other sensitive data. Sending raw PII to an LLM raises privacy and compliance concerns (GDPR, internal policies, client confidentiality).

The Solution

PII Shield sits between your documents and Claude:

1. You upload a document and select the pii-contract-analyze skill
2. PII Shield automatically anonymizes all personal data using GLiNER NER — names become <PERSON_1>, companies become <ORG_1>, etc.
3. Claude analyzes the anonymized text — writes memos, suggests edits, compares versions — never seeing the real data
4. PII Shield restores the original names back into Claude's output and saves the final document locally

Claude does the thinking. PII Shield keeps the data private.

Document -> [PII Shield: GLiNER NER] -> Anonymized text -> [Claude: Analysis] -> [PII Shield: Restore] -> Result
              Acme Corp. -> <ORG_1>                                            <ORG_1> -> Acme Corp.
              John Smith  -> <PERSON_1>                                        <PERSON_1> -> John Smith

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Quick Start

Prerequisites

• Python 3.10+ installed and in PATH
• Claude Desktop (Cowork)

Step 1: Pre-install dependencies (recommended)

Why? PII Shield requires ~1 GB of AI models and libraries (PyTorch, GLiNER, Presidio, SpaCy). If you pre-install them, the extension will start instantly. If you skip this step, PII Shield will auto-install everything on first use — but you'll need to wait 5-10 minutes while Claude shows progress updates.

Option A — Run the Python script (if you're comfortable with the command line):

python setup_pii_shield.py

The script will install all packages, download AI models, and verify everything works. Takes 3-10 minutes depending on your internet speed.

Option B — One-click installer (no command line needed):

• Windows: Download and double-click setup_pii_shield.bat
• macOS/Linux: Download setup_pii_shield.sh, then run in Terminal: chmod +x setup_pii_shield.sh && ./setup_pii_shield.sh

Both are fully self-contained — just download one file and run it.

Note: Both options require Python 3.10+ to be installed on your system. If you don't have Python, download it from python.org — make sure to check "Add Python to PATH" during installation.

Step 2: Install the extension and skill in Claude Desktop

1. Download pii-shield-v5.5.0.mcpb and pii-contract-analyze.skill
2. MCP Server: In Claude Desktop — Settings > Extensions > Advanced settings -> click Install extension -> select pii-shield-v5.5.0.mcpb
3. Skill: In Claude Desktop — Customize > Skills -> click + -> Upload a skill -> select pii-contract-analyze.skill

Step 3: Use it

1. Start a new conversation in Claude Desktop
2. Select the pii-contract-analyze skill
3. Upload a document and ask Claude what you need:

You: [attach contract.docx] Find risks from the client's perspective and suggest fixes

If you ran the pre-install script (Step 1), everything starts instantly. If not, Claude will show installation progress and ask you to type "go" when it's ready (~10 min, first time only).

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What if I didn't pre-install?

No problem. PII Shield is fully self-bootstrapping:

1. When you start a conversation with the skill, Claude will detect that dependencies are being installed
2. Claude shows progress messages ("Installing PyTorch...", "Downloading BERT model...", etc.)
3. After ~10 minutes, Claude asks you to type "go" to continue
4. From that point on, every subsequent start is instant

This only happens once. After the first install, PII Shield starts in seconds.

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Use Cases

Use case	What happens
Legal memo	Upload a contract, get risk analysis. Claude works with <ORG_1> and <PERSON_2>, PII Shield restores real names in the final .docx
Contract redline	Ask Claude to suggest tracked changes. All edits reference placeholders; restored document has real names
Bulk review	Upload up to 5 NDAs, get a comparison table. Each file gets its own prefix (D1, D2...)
Quick summary	Drop a 20-page agreement, get a structured overview without exposing any PII
Anonymize only	Just anonymize a document for external sharing, no LLM analysis needed

Features