improve-skill

name	improve-skill
description	Iteratively refine and validate agent skill markdown files by implementing them in a sandbox, running validation checks (TypeScript, linting, build, browser tests), writing tests, reflecting on errors, and updating the skill documentation until it produces error-free code. Use this skill when you need to polish a skill, refine a skill, test a skill, improve skill documentation, validate a skill, debug skill instructions, or ensure a skill works end-to-end.
metadata	{"author":"@mattwoodco","version":"1.2.0","created":"2026-02-13T00:00:00.000Z","updated":"2026-02-13T00:00:00.000Z"}

Skill Polish — Iterative Skill Refinement Loop

Takes a draft skill markdown file and iteratively implements it in a sandbox/ directory (its own git repo), validates the output, reflects on errors, updates the markdown, reverts, and retries — until the skill produces a clean, error-free implementation on a fresh run.

Quick Start

1. Point at a skill markdown file (e.g., v1-skills/auth/SKILL.md)
2. Sandbox initializes as its own git repo with a project scaffold
3. Loop: implement → validate → reflect → update markdown → revert → retry
4. Final polished skill saved to skills/<feature>/SKILL.md

How It Works

┌─────────────────────────────────────────────────────────┐
│                    SKILL POLISH LOOP                     │
│                                                         │
│  ┌──────────┐    ┌───────────┐    ┌──────────────────┐  │
│  │ IMPLEMENT │───▶│ VALIDATE  │───▶│ ERRORS FOUND?    │  │
│  │ in sandbox│    │ tsc/lint/ │    │                  │  │
│  └──────────┘    │ build/    │    │  YES ──▶ REFLECT  │  │
│       ▲          │ browser   │    │         & UPDATE  │  │
│       │          └───────────┘    │         MARKDOWN  │  │
│       │                           │         ▼         │  │
│       │                           │       REVERT      │  │
│       │                           │       SANDBOX     │  │
│       └───────────────────────────│─────────┘         │  │
│                                   │                   │  │
│                                   │  NO ──▶ FINALIZE  │  │
│                                   └──────────────────┘  │
└─────────────────────────────────────────────────────────┘

Sandbox is its own git repo — reverts are instant via git reset.

Prerequisites

• sandbox/ directory (working area — becomes its own git repo)
• skills/ directory (output for polished skills)
• Node.js / Bun runtime for validation
• Source skill markdown file to polish

Workflow Steps

Phase 0: Pre-flight Checks

Verify the environment before starting.

# Check sandbox state
ls sandbox/

# If sandbox has a git repo with baseline commit, ask user:
# "Sandbox has baseline. Reuse it or start fresh?"
cd sandbox && git log --oneline -1 2>/dev/null && cd ..

# Verify output directory exists
ls skills/

CRITICAL: The sandbox is its own git repo, completely independent of the parent project. The parent project does NOT need to be a git repository.

User decision:

• Reuse: Skip Phase 2, go straight to Phase 1 → Phase 3
• Start fresh: Wipe sandbox and re-scaffold in Phase 2

Phase 1: Select Source Skill

Agent instructions:

1. Ask: "Which skill markdown file should I polish?"
2. Accept a file path (e.g., v1-skills/auth/SKILL.md)
3. Read the source markdown completely
4. Extract FEATURE_NAME from frontmatter name: field
5. Copy source to working location:

mkdir -p skills/<FEATURE_NAME>
cp <SOURCE_PATH> skills/<FEATURE_NAME>/SKILL.md

IMPORTANT: All markdown edits happen to skills/<FEATURE_NAME>/SKILL.md. Never modify the original.

Phase 2: Initialize Sandbox Project

Skip this phase if reusing existing baseline (user chose "Reuse" in Phase 0).

Agent instructions:

1. Read skill's Prerequisites and Installation sections to determine project type
2. Clean sandbox:

rm -rf sandbox/* sandbox/.* 2>/dev/null

1. Initialize appropriate project:

# Example for Next.js:
cd sandbox && bunx create-next-app@latest . --typescript --tailwind --eslint --app --src-dir --no-import-alias --use-bun && cd ..

# Example for Node.js:
cd sandbox && bun init -y && cd ..

1. Install skill-specified dependencies
2. Verify clean build: cd sandbox && bun run build && cd ..
3. Initialize sandbox git repo and commit baseline:

cd sandbox
git init
git add -A
git commit -m "baseline: scaffold for <FEATURE_NAME>"
cd ..

This baseline enables fast reverts without touching the parent project.

Phase 3: Implementation Loop

Set ITERATION=1 and MAX_ITERATIONS=10.

---

Step 3a: Implement

Read the current working markdown (skills/<FEATURE_NAME>/SKILL.md) and follow it exactly.

Agent instructions:

1. Read the full skill markdown
2. Follow every Setup Step / Implementation instruction
3. Create all files from "What Gets Created" section
4. Run all installation commands
5. Use placeholder values for env vars
6. Do not improvise — test whether the markdown alone is sufficient

File mapping: All skill paths are relative to sandbox root:

• src/lib/auth.tsx → sandbox/src/lib/auth.tsx

Step 3b: Validate

Run the automated validation script:

./scripts/validate.sh

This script runs multi-tier validation and outputs structured error JSON. See VALIDATION.md for validation strategies.

Manual validation tiers (if not using script):

Tier 1 — TypeScript (always run):

cd sandbox && bunx tsc --noEmit 2>&1

Tier 2 — Linting (if configured):

cd sandbox && bunx biome check . 2>&1
# OR: bunx eslint . 2>&1

Tier 3 — Build (if build script exists):

cd sandbox && bun run build 2>&1

Tier 4 — Browser (if skill has TEST_PAGE.md):

# Start dev server in background
cd sandbox && bun run dev &
DEV_PID=$!
sleep 3

Use playwright-cli (runs via Bash, no MCP needed) to validate:

• playwright-cli open http://localhost:3000/<test-route> → navigate to the test route
• playwright-cli snapshot → verify elements are present in the DOM
• playwright-cli console → check for JS errors or warnings
• playwright-cli screenshot --output screenshots/<feature>.png → capture visual state
• playwright-cli click <ref> → interact with UI elements

kill $DEV_PID

Tier 5 — Test Writing (after Tiers 1-4 pass):

Once the implementation passes Tiers 1-4, write tests for the skill's code:

• Unit tests (sandbox/__tests__/unit/): utility functions, lib helpers, validators
• Integration tests (sandbox/__tests__/integration/): API routes, database queries
• Component tests (sandbox/__tests__/e2e/): UI pages via playwright-cli

cd sandbox && bun test 2>&1

Test failures feed back into the reflection loop — classify as test-failure errors and update the skill markdown with fixes (missing exports, wrong function signatures, etc.).

Collect errors into structured format:

VALIDATION_ERRORS = [
  { source: "tsc", file: "...", line: N, message: "..." },
  ...
]

Step 3c: Decision Point

If VALIDATION_ERRORS is empty: → Skip to Phase 4: Finalize

If VALIDATION_ERRORS is not empty and ITERATION < MAX_ITERATIONS: → Continue to Step 3d: Reflect

If ITERATION >= MAX_ITERATIONS: → Stop and report:

"Reached maximum iterations (10). Remaining errors: [list]. Markdown saved but may need manual refinement."

Step 3d: Reflect and Update Markdown

CRITICAL: Analyze each error and determine what the skill markdown should have said to prevent it.

Agent instructions for each error:

1. Classify the error — see ERROR_CLASSIFICATION.md for types:

   • missing-dependency — Package not in Installation section
   • missing-file — Imported file not created by skill
   • type-error — TypeScript type mismatch
   • api-change — Library API changed
   • missing-config — Config file or env var missing
   • wrong-path — File path mismatch
   • missing-step — Undocumented setup step
   • code-error — Bug in code snippet

2. Determine the fix:

   • What specific markdown change would prevent this error?
   • Add dependency? Fix snippet? Add file? Reorder steps?

3. Apply the fix to skills/<FEATURE_NAME>/SKILL.md:

   • Edit relevant section
   • Add missing dependencies to Installation
   • Fix code snippets
   • Add missing files to "What Gets Created"
   • Update import paths

Reflection comment (add to markdown):

<!-- POLISH ITERATION {N}
Errors found: {count}
Fixes applied:
- {classification}: {brief description}
-->

Step 3e: Revert Sandbox

Reset sandbox to baseline using its own git repo:

cd sandbox
git checkout -- .
git clean -fd
cd ..

Verify revert:

cd sandbox && git status --porcelain && cd ..
# Should be empty (clean working tree)

Step 3f: Increment and Loop

ITERATION = ITERATION + 1

→ Go back to Step 3a: Implement

---

Phase 4: Finalize

Implementation passed all validation. Markdown is polished.

Agent instructions:

1. Clean up markdown:

   • Remove <!-- POLISH ITERATION --> comments
   • Bump patch version in frontmatter
   • Update updated: date
   • Verify "What Gets Created" is accurate
   • Verify Installation has all packages

2. Revert sandbox one final time:

cd sandbox
git checkout -- .
git clean -fd
cd ..

1. Report to user:

Skill polished successfully!

Feature: <FEATURE_NAME>
Iterations: {ITERATION}
Output: skills/<FEATURE_NAME>/SKILL.md

Changes made during polishing:
- {summary of key fixes}

The skill markdown now produces a clean, error-free implementation.
Sandbox baseline preserved for future runs.

Acceptance Criteria

• Agent checks sandbox state (reuse baseline or start fresh)
• Agent asks user to select source skill markdown
• Agent copies source to skills/<feature>/SKILL.md (never modifies original)
• Agent initializes sandbox as its own git repo with scaffold (or reuses existing)
• Agent implements the skill exactly as written (no improvisation)
• Agent runs TypeScript, lint, build, and browser validation
• Agent writes unit/integration/e2e tests after implementation passes validation
• On errors (including test failures): agent reflects, classifies, and updates markdown
• On errors: agent reverts sandbox via git before re-implementing
• Agent loops until clean validation or max iterations
• On success: agent cleans markdown, reverts sandbox to baseline
• Final markdown at skills/<feature>/SKILL.md
• Original source markdown never modified
• Sandbox baseline preserved for future runs

Additional References

• VALIDATION.md — Validation strategies and tier details
• ERROR_CLASSIFICATION.md — Error types and markdown fix locations
• EDGE_CASES.md — Edge cases and troubleshooting guide