Free tool
Rules file converter
Write a rule once and use it in every coding agent your team runs. Paste a rule in any agent's format and get the file path and frontmatter for 11 targets, keeping when the rule applies. Formats checked against each vendor's docs on 2026-10-19. Nothing leaves your browser.
Scope: Only for matching files (app/**/*.rb, app/**/*.erb, config/**/*.rb, db/**/*.rb, lib/**/*.rb, test/**/*.rb, spec/**/*.rb)
Detected from: globs
Convert to
Save as: .cursor/rules/rails.mdc
--- globs: app/**/*.rb, app/**/*.erb, config/**/*.rb, db/**/*.rb, lib/**/*.rb, test/**/*.rb, spec/**/*.rb alwaysApply: false --- - Follow Rails naming and RESTful routes (resources); use bin/rails generate for models, migrations and controllers. - Filter input with strong parameters (params.expect, or require and permit on older apps); never pass raw params to create or update. - Change the schema only with new migrations; never edit a migration that has already run or edit schema.rb by hand. - Avoid N+1 queries with includes or preload. - Keep validations and data rules in models; keep controllers thin. - Use Hotwire (Turbo and Stimulus) for interactivity before adding a JavaScript framework. - Put background work in Active Job jobs, not in the request cycle. - Keep secrets in Rails credentials or environment variables, never in committed files. - Write tests in the project's framework (Minitest or RSpec) and run them before finishing.
Format source: Cursor docs.
How scope maps between agents
| When it applies | Cursor .mdc | Claude Code | GitHub Copilot | Kiro | Antigravity / Devin |
|---|---|---|---|---|---|
| Always on | alwaysApply: true | no paths | applyTo: "**" | inclusion: always | trigger: always_on |
| Matching files | globs | paths | applyTo | inclusion: fileMatch | trigger: glob |
| Agent decides | description | (use a Skill) | description (VS Code) | inclusion: auto | trigger: model_decision |
| Manual | no description, no globs | (use a Skill) | neither (VS Code) | inclusion: manual | trigger: manual |
AGENTS.md, GEMINI.md and Codex have no frontmatter: put the file in the folder it applies to. Zed reads only the first instruction file it finds, so a .cursorrules file wins over AGENTS.md there.
Related
Rules formats keep changing
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