000-cursor-rules

A rule for creating or updating Cursor rules, which are project instructions that guide the Cursor coding editor. It defines their format, location, naming scheme, file patterns, and required sections.

In plain words
What is it for?
Use it when adding a new Cursor rule, changing an existing one, or turning a lesson from the user into a retained project instruction.
Why use it?
It ensures rules are stored and written in a consistent format so Cursor can apply them reliably.

Cursor rule

Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

agentmods
npx agentmods add rules/andyw8/rails_rules/000-cursor-rules
Clone the repo
git clone --depth 1 https://github.com/andyw8/rails_rules
Per session 0 Nothing until a file matches its globs; then the whole rule loads.
When invoked 762 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
Origin 100% copy Near-identical to another mod in the catalogue.
Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

ModelPer sessionOnce invoked
Fable 5 $0.00000 $0.00762
Opus 5 $0.00000 $0.00381
Sonnet 5 $0.00000 $0.00152
Haiku 4.5 $0.00000 $0.00076

Measured 2d ago against content hash 4d845e47680d, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

000-cursor-rules scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 2d ago.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

Origin

This is a copy

100% identical to 000-cursor-rules — 2 lines differ, which has more behind it and is treated as the original. This page carries a canonical link to it rather than competing with it.

lib/generators/rails_rules/templates/000-cursor-rules.mdc · 114 lines

How it starts

The opening of the file, as written. The whole thing — 114 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Cursor Rules Format

Core Structure

---
description: ACTION when TRIGGER to OUTCOME
globs: *.mdc
---

# Rule Title

## Context
- When to apply this rule
- Prerequisites or conditions

## Requirements
- Concise, actionable items
- Each requirement must be testable

## Examples
<example>
Good concise example with explanation
</example>

<example type="invalid">
Invalid concise example with explanation
</example>

File Organization

Location

  • Path: .cursor/rules/
  • Extension: .mdc

Naming Convention

PREFIX-name.mdc where PREFIX is:

  • 0XX: Core standards
  • 1XX: Tool configs
  • 3XX: Testing standards
  • 1XXX: Language rules
  • 2XXX: Framework rules
  • 8XX: Workflows
  • 9XX: Templates
  • _name.mdc: Private rules

Glob Pattern Examples

Common glob patterns for different rule types:

  • Core standards: .cursor/rules/*.mdc
  • Language rules: src/**/*.{js,ts}
  • Testing standards: **/*.test.{js,ts}
  • React components: src/components/**/*.tsx
  • Documentation: docs/**/*.md
  • Configuration files: *.config.{js,json}
  • Build artifacts: dist/**/*
  • Multiple extensions: src/**/*.{js,jsx,ts,tsx}
  • Multiple files: dist//*, docs//*.md

Required Fields

Frontmatter

  • description: ACTION TRIGGER OUTCOME format
  • globs: glob pattern for files and folders

Body

  • X.Y.Z
  • context: Usage conditions
  • requirements: Actionable items
  • examples: Both valid and invalid

Formatting Guidelines

  • Use Concise Markdown primarily
  • XML tags limited to:
  • Always indent content within XML or nested XML tags by 2 spaces
  • Keep rules as short as possbile
  • Use Mermaid syntax if it will be shorter or clearer than describing a complex rule
  • Use Emojis where appropriate to convey meaning that will improve rule understanding by the AI Agent
  • Keep examples as short as possible to clearly convey the positive or negative example

AI Optimization Tips

Read the full file on GitHub · 114 lines

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

  1. 2d ago First seen · 114 lines · 0 tokens per session scan A 4d845e47680d

Subscribe to this mod's changes

000-cursor-rules is a cursor rule published in the GitHub repository andyw8/rails_rules (4 stars, last pushed 1y ago), licensed MIT. It costs nothing until one of its globs matches a file; then it loads 762 tokens. A static security scan graded it A with 0 findings. It is 100% identical to 000-cursor-rules, differing in 2 lines, and is treated as a copy.