Redact PII (emails, phones, SSNs, credit cards, AWS keys, IPs) from text before sending to LLMs via @mukundakatta/maskprompt-mcp (npx)

@mukundakatta/maskprompt-mcp — PII redaction for agent prompts (npx, stdio, no auth)

Package: @mukundakatta/maskprompt-mcp v0.1.1 on npm Launch: npx -y @mukundakatta/maskprompt-mcp (stdio transport) Auth: None — runs entirely locally, no network calls

Tools (2)

Detected PII types

EMAIL, US_PHONE, US_SSN, CREDIT_CARD (Luhn-validated), IPV4, URL, MAC_ADDRESS, IBAN, AWS_ACCESS_KEY, GITHUB_TOKEN, JWT

Masking strategies (redact only)

Recipe: Redact all PII with tag strategy

printf '{"jsonrpc":"2.0","id":1,"method":"initialize","params":{"protocolVersion":"2024-11-05","capabilities":{},"clientInfo":{"name":"agent","version":"1.0.0"}}}\n{"jsonrpc":"2.0","method":"notifications/initialized"}\n{"jsonrpc":"2.0","id":2,"method":"tools/call","params":{"name":"redact","arguments":{"text":"Contact [email protected] or 555-123-4567. SSN 123-45-6789, card 4111111111111111, IP 192.168.1.100","strategy":"tag"}}}\n' | npx -y @mukundakatta/maskprompt-mcp

Result:

{
  "masked": "Contact <EMAIL> or <US_PHONE>. SSN <US_SSN>, card <CREDIT_CARD>, IP <IPV4>",
  "matches": [
    {"kind": "EMAIL", "start": 8, "end": 28, "value": "[email protected]"},
    {"kind": "US_PHONE", "start": 32, "end": 44, "value": "555-123-4567"},
    {"kind": "US_SSN", "start": 50, "end": 61, "value": "123-45-6789"},
    {"kind": "CREDIT_CARD", "start": 68, "end": 84, "value": "4111111111111111"},
    {"kind": "IPV4", "start": 89, "end": 102, "value": "192.168.1.100"}
  ]
}

Agent pattern: refuse on detected PII

Use find_pii as a pre-flight check: if count > 0, refuse to forward the prompt to a remote LLM.

Gotchas

• GitHub token detection may miss tokens with non-standard lengths (tested ghp_ + 37 chars → not detected; the server expects the standard 36-char suffix).
• Credit card detection includes Luhn validation — random 16-digit numbers that fail Luhn won't be flagged.
• The hash strategy produces deterministic tags (SHA-256 truncated), so the same email always maps to the same <EMAIL:abc123> — useful for downstream correlation without exposing the original.