Use when creating new skills, editing existing skills, or verifying skills work before deployment

Writing Skills Overview Writing skills IS Test Driven Development applied to process documentation. Personal skills live in your runtime's skills directory ( ~/.claude/skills/ on Claude Code) — see [codex tools.md](../using superpowers/references/codex tools.md) or [gemini tools.md](../using superpowers/references/gemini tools.md) for the path on those runtimes. Codex, Copilot CLI, and Gemini CLI all also recognize ~/.agents/skills/ as a cross runtime alias. You write test cases (pressure scenarios with subagents), watch them fail (baseline behavior), write the skill (documentation), watch tests pass (agents comply), and refactor (close loopholes). Core principle: If you didn't watch an agent fail without the skill, you don't know if the skill teaches the right thing. REQUIRED BACKGROUND: You MUST understand superpowers:test driven development before using this skill. That skill defines the fundamental RED GREEN REFACTOR cycle. This skill adapts TDD to documentation. Official guidance: For Anthropic's official skill authoring best practices, see anthropic best practices.md. This document provides additional patterns and guidelines that complement the TDD focused approach in this skill. What is a Skill? A skill is a reference guide for proven techniques, patterns, or tools. Skills help future agents find and apply effective approaches. Skills are: Reusable techniques, patterns, tools, reference guides Skills are NOT: Narratives about how you solved a problem once TDD Mapping for Skills TDD Concept Skill Creation Test case Pressure scenario with subagent Production code Skill document (SKILL.md) Test fails (RED) Agent violates rule without skill (baseline) Test passes (GREEN) Agent complies with skill present Refactor Close loopholes while maintaining compliance Write test first Run baseline scenario BEFORE writing skill Watch it fail Document exact rationalizations agent uses Minimal code Write skill addressing those specific violations Watch it pass Verify agent now complies Refactor cycle Find new rationalizations → plug → re verify The entire skill creation process follows RED GREEN REFACTOR. When to Create a Skill Create when: Technique wasn't intuitively obvious to you You'd reference this again across projects Pattern applies broadly (not project specific) Others would benefit Don't create for: One off solutions Standard practices well documented elsewhere Project specific conventions (put in your instructions file) Mechanical constraints (if it's enforceable with regex/validation, automate it—save documentation for judgment calls) Skill Types Technique Concrete method with steps to follow (condition based waiting, root cause tracing) Pattern Way of thinking about problems (flatten with flags, test invariants) Reference API docs, syntax guides, tool documentation (office docs) Directory Structure Flat namespace all skills in one searchable namespace Separate files for: 1. Heavy reference (100+ lines) API docs, comprehensive syntax 2. Reusable tools Scripts, utilities, templates Keep inline: Principles and concepts Code patterns (< 50 lines) Everything else SKILL.md Structure Frontmatter (YAML): Two required fields: name and description (see [agentskills.io/specification](https://agentskills.io/specification) for all supported fields) Max 1024 characters total name : Use letters, numbers, and hyphens only (no parentheses, special chars) description : Third person, describes ONLY when to use (NOT what it does) Start with "Use when..." to focus on triggering conditions Include specific symptoms, situations, and contexts NEVER summarize the skill's process or workflow (see SDO section for why) Keep under 500 characters if possible Skill Discovery Optimization (SDO) Critical for discovery: Future agents need to FIND your skill 1. Rich Description Field Purpose: Your agent reads the description to decide which skills to load for a given task. Make it answer: "Should I read this skill right now?" Format: Start with "Use when..." to focus on triggering conditions CRITICAL: Description = When to Use, NOT What the Skill Does The description should ONLY describe triggering conditions. Do NOT summarize the skill's process or workflow in the description. Why this matters: Testing revealed that when a description summarizes the skill's workflow, an agent may follow the description instead of reading the full skill content. A description saying "code review between tasks" caused an agent to do ONE review, even though the skill's flowchart clearly showed TWO reviews (spec compliance then code quality). When the description was changed to just "Use when executing implementation plans with independent tasks" (no workflow summary), the agent correctly read the flowchart and followed the two stage review process. The trap: Descriptions that summarize workflow create a shortcut agents will take. The skill body becomes documentation agents skip. Content: Use concrete triggers, symptoms, and situations that signal this skill applies Describe the problem (race conditions, inconsistent behavior) not language specific symptoms (setTimeout, sleep) Keep triggers technology agnostic unless the skill itself is technology specific If skill is technology specific, make that explicit in the trigger Write in third person (injected into system prompt) NEVER summarize the skill's process or workflow 2. Keyword Coverage Use words an agent would search for: Error messages: "Hook timed out", "ENOTEMPTY", "race condition" Symptoms: "flaky", "hanging", "zombie", "pollution" Synonyms: "timeout/hang/freeze", "cleanup/teardown/afterEach" Tools: Actual commands, library names, file types 3. Descriptive Naming Use active voice, verb first: ✅ creating skills not skill creation ✅ condition based waiting not async test helpers 4. Token Efficiency (Critical) Problem: getting started and frequently referenced skills load into EVERY conversation. Every token counts. Target word counts: getting started workflows: <150 words each Frequently loaded skills: <200 words total Other skills: <500 words (still be concise) Techniques: Move details to tool help: Use cross references: Compress examples: Eliminate redundancy: Don't repeat what's in cross referenced skills Don't explain what's obvious from command Don't include multiple examples of same pattern Verification: Name by what you DO or core insight: ✅ condition based waiting async test helpers ✅ using skills not skill usage ✅ flatten with flags data structure refactoring ✅ root cause tracing debugging techniques Gerunds ( ing) work well for processes: creating skills , testing skills , debugging with logs Active, describes the action you're taking 5. Cross Referencing Other Skills When writing documentation that references other skills: Use skill name only, with explicit requirement markers: ✅ Good: REQUIRED SUB SKILL: Use superpowers:test driven development ✅ Good: REQUIRED BACKGROUND: You MUST understand superpowers:systematic debugging ❌ Bad: See skills/testing/test driven development (unclear if required) ❌ Bad: @skills/testing/test driven development/SKILL.md (force loads, burns context) Why no @ links: @ syntax force loads files immediately, consuming 200k+ context before you need them. Flowchart Usage Use flowcharts ONLY for: Non obvious decision points Process loops where you might stop too early "When to use A vs B" decisions Never use flowcharts for: Reference material → Tables, lists Code examples → Markdown blocks Linear instructions → Numbered lists Labels without semantic meaning (step1, helper2) See graphviz conventions.dot in this directory for graphviz style rules. Visualizing for your human partner: Use render graphs.js in this directory to render a skill's flowcharts to SVG: Code Examples One excellent example beats many mediocre ones Choose most relevant language: Testing techniques → TypeScript/JavaScript System debugging → Shell/Python Data processing → Python Good example: Complete and runnable Well commented explaining WHY From real scenario Shows pattern clearly Ready to adapt (not generic template) Don't: Implement in 5+ languages Create fill in the blank templates Write contrived examples You're good at porting one great example is enough. File Organization Self Contained Skill When: All content fits, no heavy reference needed Skill with Reusable Tool When: Tool is reusable code, not just narrative Skill with Heavy Reference When: Reference material too large for inline The Iron Law (Same as TDD) This applies to NEW skills AND EDITS to existing skills. Write skill before testing? Delete it. Start over. Edit skill without testing? Same violation. No exceptions: Not for "simple additions" Not for "just adding a section" Not for "documentation updates" Don't keep untested changes as "reference" Don't "adapt" while running tests Delete means delete REQUIRED BACKGROUND: The superpowers:test driven development skill explains why this matters. Same principles apply to documentation. Testing All Skill Types Different skill types need different test approaches: Discipline Enforcing Skills (rules/requirements) Examples: TDD, verification before completion, designing before coding Test with: Academic questions: Do they understand the rules? Pressure scenarios: Do they comply under stress? Multiple pressures combined: time + sunk cost + exhaustion Identify rationalizations and add explicit counters Success criteria: Agent follows rule under maximum pressure Technique Skills (how to guides) Examples: condition based waiting, root cause tracing, defensive programming Test with: Application scenarios: Can they apply the technique correctly? Variation scenarios: Do they handle edge cases? Missing information tests: Do instructions have gaps? Success criteria: Agent successfully applies technique to new scenario Pattern Skills (mental models) Examples: reducing complexity, information hiding concepts Test with: Recognition scenarios: Do they recognize when pattern applies? Application scenarios: Can they use the mental model? Counter examples: Do they know when NOT to apply? Success criteria: Agent correctly identifies when/how to apply pattern Reference Skills (documentation/APIs) Examples: API documentation, command references, library guides Test with: Retrieval scenarios: Can they find the right information? Application scenarios: Can they use what they found correctly? Gap testing: Are common use cases covered? Success criteria: Agent finds and correctly applies reference information Common Rationalizations for Skipping Testing Excuse Reality "Skill is obviously clear" Clear to you ≠ clear to other agents. Test it. "It's just a reference" References can have gaps, unclear sections. Test retrieval. "Testing is overkill" Untested skills have issues. Always. 15 min testing saves hours. "I'll test if problems emerge" Problems = agents can't use skill. Test BEFORE deploying. "Too tedious to test" Testing is less tedious than debugging bad skill in production. "I'm confident it's good" Overconfidence guarantees issues. Test anyway. "Academic review is enough" Reading ≠ using. Test application scenarios. "No time to test" Deploying untested skill wastes more time fixing it later. All of these mean: Test before deploying. No exceptions. Match the Form to the Failure

writing-skills