rule-gen

Stop writing Cursor rules by hand.

Feed your codebase to Gemini. Get rules based on patterns it finds in your code, not generic templates from a package.json scan.

export GEMINI_API_KEY=your-key-here
npx rulegen-ai

Get a free API key at aistudio.google.com/apikey.

What you get

$ npx rulegen-ai ./my-express-api

Scanning ./my-express-api...
  Found 47 files · Selected 32 for analysis · ~89,200 tokens

Generating rules with gemini-2.5-flash-lite...

Written 7 files:
  ✓ .cursor/rules/zod-validation-before-handlers.mdc
  ✓ .cursor/rules/prisma-singleton-import.mdc
  ✓ .cursor/rules/consistent-error-response-shape.mdc
  ✓ .cursor/rules/route-file-structure.mdc
  ✓ .cursor/rules/barrel-exports-from-src.mdc
  ✓ .cursor/rules/test-naming-convention.mdc
  ✓ .cursor/rules/middleware-ordering.mdc

Not "use TypeScript" or "write clean code". Rules like:

• "Import prisma from ../db — never instantiate PrismaClient directly"
• "Route files validate with Zod schemas before handlers, return { data } or { error } shapes"
• "Tests live in __tests__/ and mirror the src/ directory structure"

Output formats

Format	Flag	Output
Cursor	--format cursor (default)	.cursor/rules/*.mdc
Claude Code	--format claude-md	CLAUDE.md
AGENTS.md	--format agents-md	AGENTS.md
GitHub Copilot	--format copilot	.github/copilot-instructions.md
Windsurf	--format windsurf	.windsurfrules

How it works

1. Scans your project tree (respects .gitignore, skips binaries)
2. Detects your stack — Node.js, Python frameworks (Django, Flask, FastAPI), testing tools, linters, type checkers
3. Prioritizes config files, entry points, routes, and pattern-rich files to fit Gemini's context window
4. Sends everything in one request — Gemini's 1M token context sees your whole codebase at once. No chunking, no lost context.
5. Writes valid rule files in your chosen format

Language & framework support

rule-gen auto-detects:

Python

• Frameworks: Django, Flask, FastAPI, Tornado, Sanic, and 10+ more
• Testing: pytest, unittest, nose, tox, coverage
• Type checking: mypy, pyright, pyre, pytype
• Linting: ruff, flake8, pylint, black, isort, bandit
• Package managers: Poetry, Pipenv, pip, setuptools

Node.js/TypeScript

• Detects from package.json dependencies
• Identifies module type (ESM/CommonJS)

This context helps Gemini generate rules specific to your stack — e.g., Django best practices for Django projects, FastAPI patterns for FastAPI apps.

Options

--format <format>   cursor, claude-md, agents-md, copilot, windsurf
--model <model>     Gemini model (default: gemini-2.5-flash-lite)
--dry-run           Preview without writing files
--verbose           Show which files are sent
--max-files <n>     Max source files (default: 50)
--api-key <key>     Or set GEMINI_API_KEY env var

Zero dependencies. Built with Node.js builtins only.

Next step: check your rules

rule-gen creates rules. cursor-doctor makes sure they actually work.

npx cursor-doctor scan    # Health check with letter grade
npx cursor-doctor lint    # Detailed rule-by-rule linting

100+ checks for broken globs, vague instructions, conflicts, and token waste. Also: rule-porter converts rules between Cursor, Claude, Copilot, and Windsurf.

License

MIT