Rules

Rules are coding standards and guidelines that the client applies based on file type or path. Unlike skills, rules do not wait to be triggered — they're always on when their scope matches.

A rule codifies a standard, convention, or constraint that should apply automatically whenever the client is working in a matching context — a file type, a directory, or a whole repository.

Where a skill loads when its description matches the user's goal, a rule loads when its scope matches the current file or context. Rules are the "standing orders" of the AI client.

When to use a rule

• Enforcing a coding convention: "Always use pytest with database reuse. Mock external HTTP calls with vcrpy."

• Requiring a specific pattern: "When adding a new Django model, also update the factories module and write a migration test."

• Reminding the client to load another asset: "Load the frontend-design skill whenever editing files under frontend/."

Directory layout

A rule follows the same packaging conventions as a skill — a directory with a markdown file and frontmatter. The convention is RULE.md with a description, plus optional scope metadata:

---
name: testing
description: >-
  Enforce testing best practices: load the test-writer skill, use pytest with
  database reuse, leverage fixtures and factories, and mock external calls
  with vcrpy.
globs: "**/*.py"
---

# Testing rules

- Use pytest with `--reuse-db` unless migrations changed.
- Prefer factories (`factory_boy`) over ad-hoc dict fixtures.
- Mock HTTP calls with `vcrpy`; commit cassettes alongside tests.
- Load the `test-writer` skill when writing new tests.

globs tells the client which files the rule applies to. It maps to Cursor's rule-glob format and the equivalents in other clients.

Rules vs skills

	Skill	Rule
Loading trigger	Description matches user prompt	Scope (file type / path) matches current context
On by default?	No — model decides	Yes — whenever scope matches
Typical content	How to do a task	What to always remember or enforce
Typical size	1–10k tokens	A few hundred tokens

If you find yourself writing a rule that's 20k tokens long, you probably want a skill referenced by a short rule instead.

Creating a rule

Same three entry points as any other asset: the home-page assistant, the Create → Rule button, or sx add ~/.cursor/rules/testing.

Client compatibility

Rules are supported in Claude Code, Cursor, GitHub Copilot, Gemini (CLI / VS Code / JetBrains / Android Studio), Cline, and Kiro. The rule file lands under each client's rules directory (e.g. .cursor/rules/, .claude/CLAUDE.md fragments) at install time.

Discovered rules

Sleuth Skills can discover existing rules in connected repositories and offer to promote them to vault-managed assets. The Asset list marks these entries with Source: <repo> so you know where they came from. This is the fastest way to bring pre-existing .cursor/rules/ and .github/copilot-instructions.md into central management.