Skill Creator

Skill Creator is the official Anthropic meta-skill for building, testing, and refining Claude agent skills with the same rigor you would apply to production software. Instead of writing a SKILL.md by hand and hoping it works, Skill Creator walks you through a structured lifecycle: capture what the skill should do, draft the instructions, generate realistic test prompts, run evaluations, collect quantitative benchmarks, and iterate until the skill reliably performs across diverse inputs. The evaluation system is where this skill earns its keep. You define test prompts and expected outcomes, and Skill Creator spawns independent subagents that execute each eval in a clean context -- no cross-contamination between runs, no token bleed. Every eval runs in parallel with both a with-skill and a baseline (without-skill or previous-version) configuration, producing side-by-side comparisons. A grader agent scores each output against your assertions, an analyzer agent surfaces hidden patterns in the benchmark data, and a comparator agent can perform blind A/B judging between skill versions so you know which iteration actually performs better, not just which one feels better. Benchmark reports track pass rates, token usage (mean plus standard deviation), and elapsed time across iterations, giving you the hard numbers to decide whether a change helped or hurt. The built-in eval viewer renders all outputs, grades, and feedback in a browser-based interface where you can review results qualitatively and leave per-eval comments that feed directly into the next improvement cycle. Skill Creator also handles description optimization -- the often-overlooked step that determines whether Claude actually triggers your skill when it should. It generates 20 realistic test queries (a mix of should-trigger and should-not-trigger), runs them against your current description, and suggests refinements that reduce both false positives and false negatives. Anthropic reported improved triggering accuracy across 5 of 6 public document-creation skills using this approach. With over 10,000 installs and Anthropic-verified status, Skill Creator is the standard starting point for anyone serious about building skills that survive model updates and perform consistently across Claude.ai, Claude Code, and the API.