The test-mode rule Firebase suggests (request.time < timestamp.date(...)) leaves every document open to anyone until that date. This skill finds that and six other rule mistakes in firestore.rules, storage.rules and database.rules.json, and tells you how to fix each one.

Your agent runs a scanner on your Firebase rules files. It understands match blocks, recursive wildcards, conditions over several lines, comments and helper functions, and Realtime Database JSON rules. It returns BLOCK, REVIEW, or NOT FLAGGED, with the file, line, reason, and a safer approach.

What it checks

BLOCK (fix before shipping)

• F01: a write rule with no condition or if true

• F02: a catch-all match /{document=**} or database root rule that opens everything

• F03: leftover test-mode rules (request.time < timestamp.date)

REVIEW (check before release)

• F11: writes allowed for any signed-in user

• F12: public reads with no condition

• F13: Storage uploads with no size limit

• F14: no rules_version = '2'

What's included

• The scanner (Python 3.9+, standard library only)

• A rules guide with the reason and safer approach for each rule

• Risky and safe example rules files, and the real report the scanner produces on the risky ones

Limits

It reads the rules text and does not evaluate helper functions or data in your database. Test your rules in the Firebase Emulator too. NOT FLAGGED is not a guarantee.

Contents

One ZIP file with 11 files: SKILL.md, the scanner in scripts/ (2 Python files), references/rules.md (every rule with its reason and safer approach), and examples/ (6 example files plus report.md, the real scanner output on the risky example).

How to use: This is an agent skill: a folder with a SKILL.md file and Python scripts that an AI coding agent such as Claude Code, Cursor, or Codex CLI can run. Unzip it into your agent's skills folder (for Claude Code: ~/.claude/skills/), then ask your agent to check your project. The scripts also run on their own with Python 3.9 or newer, with nothing to install. They read your files only: no network access, and nothing is sent anywhere.