Rule Updater Skill

This skill enables programmatic reading, updating, and creation of Cursor rules based on patterns extracted from PRs, issues, and user interactions.

When to Use

Use this skill when:

• Updating existing rules with new examples or patterns

• Creating new rules for emerging patterns

• Identifying when rules need updating

• Testing rule effectiveness

• Organizing and maintaining rules

Key Capabilities

1. Read Existing Rules

Read and parse rule files:

• Read .cursor/rules/*.mdc files

• Parse frontmatter (description, alwaysApply, references)

• Extract content sections

• Understand rule structure

Example:

Read a rule file

rule_content = read_file(".cursor/rules/common-mistakes.mdc")

Parse frontmatter

Extract sections

Understand structure

2. Identify When Rules Need Updating

Detect update opportunities:

• New patterns that fit existing rules

• Examples that should be added

• Clarifications needed

• Outdated information

Signals:

• Multiple PRs/issues showing same pattern

• User corrections revealing gaps

• Review feedback indicating missing guidance

• Emerging patterns not covered

3. Update Existing Rules

Process for updating:

• Read the rule file

• Identify where to add new content

• Add examples or sections

• Maintain organization

• Update references if needed

• Write updated rule

Update types:

• Add examples: Add new examples to existing sections

• Enhance sections: Expand existing sections with more detail

• Add sections: Add new sections for new patterns

• Update references: Add links to related rules/PRs/issues

Example update:

Using Deprecated Functions

Problem: Using functions that have been deprecated or removed.

Examples from PR #3567:

• ❌ Used postprocess_conversation() which was deprecated
• ❌ Assumed functions exist without checking current codebase state

NEW EXAMPLE from PR #3621:

• ❌ Used old_function() which was removed in PR #3400

4. Create New Rules

Process for creating:

• Identify the pattern category

• Collect 2-3 examples from PRs/issues/interactions

• Determine rule file name and location

• Write rule following format

• Add frontmatter with appropriate metadata

• Link from related rules

Rule structure:

description: "Brief description" alwaysApply: true/false references:

• related-file.md

Rule Title

Section 1

Content...

Section 2

Content...

Related Rules

• Link to related rules

Example new rule:

description: "Guidelines for handling background operations" alwaysApply: true

Background Operations

Features should work when app is closed/backgrounded.

Common Mistakes

• Features that only work when app is open (#4355)
• Features that require specific screen to be active

How to Avoid

• Design features to work in background
• Test with app closed/backgrounded
• Use background services where appropriate

5. Test Rule Effectiveness

Verify updates don't break guidance:

• Check rule syntax is valid

• Verify frontmatter is correct

• Ensure links work

• Test rule readability

Metrics to track:

• How often rule prevents mistakes

• Reduction in related issues after rule creation

• Rule coverage (scenarios covered)

• User feedback on rule usefulness

Rule File Format

Frontmatter

description: "Brief description of what the rule covers" alwaysApply: true # or false references:

• related-file.md
• docs/doc/example.mdx globs:
• "backend/**/*.py" # Optional: file patterns

Content Structure

Rule Title

Brief introduction explaining the rule.

Section 1

Content with examples, code snippets, etc.

Section 2

More content...

Related Rules

• .cursor/rules/related-rule.mdc - Description

Related Cursor Resources

Skills

• .cursor/skills/related-skill/SKILL.md - Description

Commands

• /related-command - Description

Update Patterns

Adding Examples

When: New examples of existing patterns emerge

How:

• Find relevant section

• Add example with source (PR/issue number)

• Maintain formatting consistency

• Keep examples organized

Example:

Common Mistake

Example from PR #3567:

• ❌ Description of mistake

Example from Issue #4394:

• ❌ Description of mistake

Enhancing Sections

When: Section needs more detail or clarification

How:

• Expand existing content

• Add more specific guidance

• Include more examples

• Add "How to avoid" subsections

Adding Sections

When: New pattern category emerges

How:

• Add new section with appropriate heading

• Follow existing section format

• Include examples

• Add to table of contents if applicable

Rule Organization

Rule Categories

Common categories:

• Common mistakes

• Architecture patterns

• Implementation checklists

• Verification guidelines

• Communication best practices

• Domain-specific patterns (Omi, backend, Flutter, etc.)

Naming Conventions

Rule file names:

• Use kebab-case: common-mistakes.mdc

• Be descriptive: pre-implementation-checklist.mdc

• Group related: backend-architecture.mdc , backend-api-patterns.mdc

Linking Rules

Cross-references:

• Link related rules in "Related Rules" section

• Reference from other rules when relevant

• Keep links updated when rules are renamed

Best Practices

• Be specific: Include concrete examples, not vague patterns

• Reference sources: Always note which PR/issue/interaction the lesson came from

• Maintain organization: Keep rules well-organized and easy to navigate

• Test updates: Verify rule updates don't break existing guidance

• Prioritize: Focus on patterns that cause the most problems

• Iterate: Rules should improve over time as more data is collected

Example Workflow

Updating a rule with new pattern:

• Identify pattern: "Multiple PRs show missing context issue"

• Read rule: Read .cursor/rules/context-communication.mdc

• Find section: Find "PR Description Requirements" section

• Add example: Add example from recent PR

• Enhance guidance: Expand "What to Include" subsection

• Update references: Add link to new PR if relevant

• Write rule: Save updated rule file

• Verify: Check syntax and links

Creating new rule:

• Identify pattern: "New pattern: Background operation issues"

• Collect examples: Gather 2-3 examples from issues/PRs

• Determine name: background-operations.mdc

• Write rule: Create rule following format

• Add frontmatter: Include description, alwaysApply, references

• Link from related: Add link from common-mistakes.mdc

• Test: Verify rule is valid and readable

Related Cursor Resources

Rules

• .cursor/rules/common-mistakes.mdc

• Common mistakes rule

• .cursor/rules/context-communication.mdc

• Communication rule

• .cursor/rules/pre-implementation-checklist.mdc

• Checklist rule

Skills

• .cursor/skills/self-improvement/SKILL.md
• Self-improvement meta-skill

Commands

• /learn-from-pr

• Analyze PR for lessons

• /self-improve

• Analyze patterns and update rules