skill-creator-plus-marketplace

Skill Creator Plus

The skill that builds skills. Write a draft, run evals against a baseline, review results in an interactive viewer, improve, and repeat — until your skill actually works. Based on Anthropic's official skill-creator plugin, with bug fixes and best practices baked in.

	Official skill-creator	skill-creator-plus
Best practices guide	—	580-line Anthropic patterns reference
Eval viewer in Cowork	Silent fail on submit	Copyable JSON textarea (fixed)
Description optimizer	Requires separate ANTHROPIC_API_KEY	Uses your existing claude session
Benchmarking script	Silent empty results	Fixed directory handling
Skill type taxonomy	3 broad categories	3 + 9 Anthropic internal types
Pre-packaging checklist	—	Official checklist built in

Why This Over the Built-in?

Anthropic ships a skill-creator plugin. It's good, but several parts are broken or missing:

• Best practices guide included — 580 lines of patterns, structural templates, troubleshooting guide, and checklists extracted from Anthropic's Complete Guide to Building Skills for Claude and Thariq's Lessons from Building Claude Code Skills. The built-in doesn't ship any of this.
• Eval viewer actually works in Cowork — the built-in silently fails: you write feedback, click "Submit All Reviews", it says "saved" — but nothing reaches Claude. This version reliably shows copyable JSON you can paste back.
• Description optimizer doesn't crash — the built-in calls the Anthropic SDK directly, requiring a separate ANTHROPIC_API_KEY most users don't have. This version uses claude -p, which just works with your existing session.
• Benchmarking script fixed — the built-in's aggregation script silently produces empty results due to undocumented directory structure requirements. Fixed and tested.

See the CHANGELOG for the full list of fixes.

Quick Start

Install (Claude Code):

claude plugin marketplace add https://github.com/yaniv-golan/skill-creator-plus
claude plugin install skill-creator-plus@skill-creator-plus-marketplace

Then just ask:

/skill-creator-plus Create a skill that reviews pull requests for security issues

The skill takes it from there — intent capture, drafting, test cases, evaluation, and iteration.

Note: If you also have Anthropic's built-in skill-creator installed, Claude may pick that one instead. Either uninstall the built-in, or use /skill-creator-plus to invoke this version explicitly.

How It Works

1. Create

Captures your intent through structured questions, researches existing patterns, then writes a SKILL.md with metadata, instructions, and test cases.

2. Evaluate

Spawns parallel runs (with-skill and baseline) on test prompts. While runs execute, drafts quantitative assertions. Grades results via the grader agent and shows them in an interactive browser-based viewer.

3. Improve

Analyzes evaluation results, identifies weaknesses, and rewrites the skill. Each iteration is benchmarked against the previous version.

4. Compare

For rigorous validation, runs blind A/B comparison: the comparator agent scores two outputs without knowing which skill produced them, then the analyzer agent unblinds and explains the differences.

5. Optimize Description

Generates trigger/non-trigger test queries, runs an optimization loop with train/test split, and selects the best-performing description.

Installation

Claude Desktop

— or install manually —

1. Click Customize in the sidebar
2. Click Browse Plugins
3. Go to the Personal tab and click +
4. Choose Add marketplace
5. Type yaniv-golan/skill-creator-plus and click Sync

Claude Code (CLI)

From your terminal:

claude plugin marketplace add https://github.com/yaniv-golan/skill-creator-plus
claude plugin install skill-creator-plus@skill-creator-plus-marketplace