AGENTS.md Improver

Audit, evaluate, and improve AGENTS.md files across a codebase to ensure Codex has optimal project instructions.

This skill can write to AGENTS.md files. After presenting a quality report and getting user approval, it updates AGENTS.md files with targeted improvements.

Workflow

Phase 1: Discovery

Find all AGENTS.md files in the repository:

find . -name "AGENTS.md" 2>/dev/null | head -50

File Types & Locations:

Type	Location	Purpose
Project root	./AGENTS.md	Primary Codex instructions (checked into git, shared with team)
Package-specific	./packages/*/AGENTS.md	Module-level instructions in monorepos
Subdirectory	Any nested location	Feature/domain-specific instructions

Note: Codex reads AGENTS.md instructions from the repository context. Nested AGENTS.md files can provide more specific instructions for subdirectories when present.

Phase 2: Quality Assessment

For each AGENTS.md file, evaluate against quality criteria. See references/quality-criteria.md for detailed rubrics.

Quick Assessment Checklist:

Criterion	Weight	Check
Commands/workflows documented	High	Are build/test/deploy commands present?
Architecture clarity	High	Can Codex understand the codebase structure?
Non-obvious patterns	Medium	Are gotchas and quirks documented?
Conciseness	Medium	No verbose explanations or obvious info?
Currency	High	Does it reflect current codebase state?
Actionability	High	Are instructions executable, not vague?

Quality Scores:

• A (90-100): Comprehensive, current, actionable
• B (70-89): Good coverage, minor gaps
• C (50-69): Basic info, missing key sections
• D (30-49): Sparse or outdated
• F (0-29): Missing or severely outdated

Phase 3: Quality Report Output

ALWAYS output the quality report BEFORE making any updates.

Format:

## AGENTS.md Quality Report

### Summary
- Files found: X
- Average score: X/100
- Files needing update: X

### File-by-File Assessment

#### 1. ./AGENTS.md (Project Root)
**Score: XX/100 (Grade: X)**

| Criterion | Score | Notes |
|-----------|-------|-------|
| Commands/workflows | X/20 | ... |
| Architecture clarity | X/20 | ... |
| Non-obvious patterns | X/15 | ... |
| Conciseness | X/15 | ... |
| Currency | X/15 | ... |
| Actionability | X/15 | ... |

**Issues:**
- [List specific problems]

**Recommended additions:**
- [List what should be added]

#### 2. ./packages/api/AGENTS.md (Package-specific)
...

Phase 4: Targeted Updates

After outputting the quality report, ask user for confirmation before updating.

Update Guidelines (Critical):

1. Propose targeted additions only - Focus on genuinely useful info:

   • Commands or workflows discovered during analysis
   • Gotchas or non-obvious patterns found in code
   • Package relationships that weren't clear
   • Testing approaches that work
   • Configuration quirks

2. Keep it minimal - Avoid:

   • Restating what's obvious from the code
   • Generic best practices already covered
   • One-off fixes unlikely to recur
   • Verbose explanations when a one-liner suffices

3. Show diffs - For each change, show:

   • Which AGENTS.md file to update
   • The specific addition (as a diff or quoted block)
   • Brief explanation of why this helps future sessions

Diff Format:

### Update: ./AGENTS.md

**Why:** Build command was missing, causing confusion about how to run the project.

```diff
+ ## Quick Start
+
+ ```bash
+ npm install
+ npm run dev  # Start development server on port 3000
+ ```

### Phase 5: Apply Updates

After user approval, apply changes using the Edit tool. Preserve existing content structure.

## Templates

See [references/templates.md](references/templates.md) for AGENTS.md templates by project type.

## Common Issues to Flag

1. **Stale commands**: Build commands that no longer work
2. **Missing dependencies**: Required tools not mentioned
3. **Outdated architecture**: File structure that's changed
4. **Missing environment setup**: Required env vars or config
5. **Broken test commands**: Test scripts that have changed
6. **Undocumented gotchas**: Non-obvious patterns not captured

## User Tips to Share

When presenting recommendations, remind users:

- **Keep it concise**: AGENTS.md is part of the agent prompt; dense is better than verbose
- **Actionable commands**: All documented commands should be copy-paste ready
- **Use scoped instructions**: Prefer nested AGENTS.md files only when a subdirectory genuinely needs different guidance

## What Makes a Great AGENTS.md

**Key principles:**
- Concise and human-readable
- Actionable commands that can be copy-pasted
- Project-specific patterns, not generic advice
- Non-obvious gotchas and warnings

**Recommended sections** (use only what's relevant):
- Commands (build, test, dev, lint)
- Architecture (directory structure)
- Key Files (entry points, config)
- Code Style (project conventions)
- Environment (required vars, setup)
- Testing (commands, patterns)
- Gotchas (quirks, common mistakes)
- Workflow (when to do what)