pii-mcp

Pattern-based PII scrubbing for MCP servers (regex + checksums). Masks emails, IBANs, cards, BICs, MACs, IMEIs, IPs, coordinates, BSNs, US SSNs, German tax IDs, Dutch BTW-ids, Dutch passport/ID numbers, phones, Dutch postcodes, and Dutch license plates in tool results. Not NER for person names or full street addresses. Language packs: en, nl, and opt-in de.

Example

from pii_mcp import scrub_text

scrub_text(
    "Contact ada@example.com. IBAN NL91 ABNA 0417 1643 00. card 4111111111111111"
)
# Contact [EMAIL]. IBAN [IBAN]. card [CREDIT_CARD]

Install

pip install "pii-mcp[fastmcp]"   # FastMCP >= 3.0.0
# or
pip install pii-mcp              # core; platform wheels include Rust acceleration
# or
npm install pii-mcp

FastMCP

from fastmcp import FastMCP
from pii_mcp.fastmcp import PiiScrubMiddleware

mcp = FastMCP("MyServer")
mcp.add_middleware(PiiScrubMiddleware())  # languages=["en", "nl"] by default
# mcp.add_middleware(PiiScrubMiddleware(languages=["en", "nl", "de"]))

Results only. On scrub failure or oversize, the result is withheld, never forwarded unmasked.

Core

from pii_mcp import scrub_text, scrub_payload

scrub_text("mail ada@example.com")
scrub_payload({"email": "ada@example.com"}, languages=["en"])

Scope

Aligned with AP: wat zijn persoonsgegevens where pattern/checksum detection can reach them. Names, free-text health data (allergies), photos/audio/video, unstructured klant-/personeelsnummers, and full street addresses need NER or media handling and stay out of scope.

AP coverage (pattern layer)

Packages

Rust core (Python)

Published platform wheels ship pii_mcp._native (PyO3 over pii-core). Pip prefers those on supported OS/arch; elsewhere (or with --no-binary) you get the pure-Python hatchling wheel/sdist and the same scrub API.

When _native is importable, scrub_text / scrub_payload use it. Force the Python path with PII_MCP_BACKEND=python; require native with PII_MCP_BACKEND=native.

Local development from a clone (optional):

pip install -e ".[native]"
maturin develop --release --manifest-path crates/pii-mcp-native/Cargo.toml

Performance (Python vs Rust release)

Medians from scripts/bench_backends.py on macOS arm64 / CPython 3.14.7 (release native build; debug builds are not representative):

python scripts/bench_backends.py