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 references/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 Writing SKILL.md A skill's description says only when to use it: triggering conditions and symptoms, starting with "Use when...". It never summarizes the skill's workflow, because an agent that reads a workflow summary follows it instead of reading the skill. When you write or change a skill's frontmatter, name or description, or need to cut its size, read [references/discovery.md](references/discovery.md): the SKILL.md template, description and keyword guidance, naming, token budgets, and cross referencing other skills. Flowcharts When you add or change a flowchart in a skill, read [references/flowcharts.md](references/flowcharts.md) first: when a flowchart earns its place, the graphviz conventions, and how to render one. 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 Invoke bundled scripts through their interpreter in the prose ( bash scripts/tool.sh , node scripts/tool.js ), never by bare path: some harness plugin packagers strip executable bits, and a bare scripts/tool.sh fails there with Permission denied . 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 Before writing guidance, classify the baseline failure. The form that bulletproofs one failure type measurably backfires on another. Baseline failure Right form Wrong form Skips/violates a rule under pressure (knows better, does it anyway) Prohibition + rationalization table + red flags (see references/bulletproofing.md) Soft guidance ("prefer...", "consider...") Complies, but output has the wrong shape (bloated prompt, buried verdict, restated spec) Positive recipe or contract: state what the output IS — its parts, in order Prohibition list ("don't restate", "never narrate") Omits a required element from something they already produce Structural: REQUIRED field or slot in the template they fill in Prose reminders near the template Behavior should depend on a condition Conditional keyed to an observable predicate ("if the brief exists, reference it") Unconditional rule + exemption clauses Why prohibitions backfire on shaping problems: under a competing incentive ("make the prompt self contained"), agents negotiate with "don't X". In head to head wording tests on dispatch prompt guidance, the prohibition arm produced clearly more of the unwanted content than the recipe arm (fully separated distributions), and trended worse than even the no guidance control — micro test your own case rather than assuming, but never reach for the prohibition by default. A recipe leaves nothing to negotiate: the output matches the stated shape or it doesn't. Rules for whichever form you pick: No nuance clauses. "Don't X unless it matters" reopens the negotiation — appending a single nuance clause to a winning recipe degraded it from consistent to noisy in the same wording tests. Express a real exception as its own conditional on an observable predicate. Exemption clauses don't scope. "This limit doesn't apply to code blocks" still suppresses code blocks. If part of the output must be exempt, restructure so the rule can't reach it. Bulletproofing Against Rationalization When the baseline failure is a discipline failure, read [references/bulletproofing.md](references/bulletproofing.md) before you write the guidance: closing loopholes, the spirit vs letter line, the rationalization table, and the red flags list. RED GREEN REFACTOR for Skills Follow the TDD cycle: RED: Write Failing Test (Baseline) Run pressure scenario with subagent WITHOUT the skill. Document exact behavior: What choices did they make? What rationalizations did they use (verbatim)? Which pressures triggered violations? This is "watch the test fail" you must see what agents naturally do before writing the skill. GREEN: Write Minimal Skill Write skill that addresses those specific rationalizations. Don't add extra content for hypothetical cases. Run same scenarios WITH skill. Agent should now comply. REFACTOR: Close Loopholes Agent found new rationalization? Add explicit counter. Re test until bulletproof. Micro Test Wording Before Full Scenarios Full pressure scenario runs are the final gate, but they are slow and expensive per iteration. Verify the wording itself first with micro tests: 1. One fresh context sample per call — a raw API call, or a single shot subagent if you don't have API access. System prompt = the realistic context the guidance will live in (the full skill or prompt template, not the guidance in isolation); user message = a task that tempts the failure. 2. Always include a no guidance control. If the control doesn't exhibit the failure, there is nothing to fix — stop, don't author the guidance. 3. 5+ reps per variant. Single samples lie. 4. Manually read every flagged match. Score programmatically if you like, but template echoes and quoted counter examples masquerade as hits; automated counts alone overstate both failure and success. 5. Variance is a metric. When g

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