Writing Skills

Overview

Writing skills IS Test-Driven Development applied to process documentation.

Personal skills live in agent-specific directories (
~/.claude/skills
for Claude Code,
~/.agents/skills/
for Codex)

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 core-engineering:test-driven-development before using this skill. That skill defines the fundamental RED-GREEN-REFACTOR cycle. This skill adapts TDD to documentation.

Authoring standard: Use references/skill-standards/README.md as the source of truth for naming, frontmatter, trigger contracts, progressive disclosure, metadata parity, and example quality.

What is a Skill?

A skill is a reference guide for proven techniques, patterns, or tools. Skills help future Claude instances 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 CLAUDE.md)
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)

Authoring Standard

Use references/skill-standards/README.md as the single source of truth for:

```
NAME-01
```
and
```
FRONTMATTER-01
```
for skill naming and frontmatter
```
TRIGGER-01
```
,
```
TRIGGER-02
```
, and
```
SEARCH-01
```
for descriptions and discoverability
```
STRUCTURE-01
```
and
```
STRUCTURE-02
```
for what belongs in
```
SKILL.md
```
```
DISCLOSURE-01
```
,
```
TOPOLOGY-01
```
, and
```
TOPOLOGY-02
```
for supporting files
```
EXAMPLE-01
```
,
```
METADATA-01
```
, and
```
RUNTIME-01
```
for examples and runtime parity

Load that file before drafting or refactoring any skill. This skill focuses on the TDD workflow that proves those rules actually work under pressure.

Optional Authoring Patterns

These are implementation aids, not the source of truth:

Use small flowcharts only for non-obvious decisions or loops where agents commonly stop too early.
Prefer one excellent example over multi-language dilution.
Use
```
graphviz-conventions.dot
```
in this directory for diagram styling when you truly need a flowchart.
Use
```
render-graphs.js
```
to render diagrams for human review when needed.

The Iron Law (Same as TDD)

NO SKILL WITHOUT A FAILING TEST FIRST

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 core-engineering: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.

Bulletproofing Skills Against Rationalization

Skills that enforce discipline (like TDD) need to resist rationalization. Agents are smart and will find loopholes when under pressure.

Psychology note: Understanding WHY persuasion techniques work helps you apply them systematically. See persuasion-principles.md for research foundation (Cialdini, 2021; Meincke et al., 2025) on authority, commitment, scarcity, social proof, and unity principles.

Close Every Loophole Explicitly

Don't just state the rule - forbid specific workarounds:

<Bad> ```markdown Write code before test? Delete it. ``` </Bad> <Good> ```markdown Write code before test? Delete it. Start over.

No exceptions:

Don't keep it as "reference"
Don't "adapt" it while writing tests
Don't look at it
Delete means delete

</Good>

### Address "Spirit vs Letter" Arguments

Add foundational principle early:

```markdown
**Violating the letter of the rules is violating the spirit of the rules.**

This cuts off entire class of "I'm following the spirit" rationalizations.

Build Rationalization Table

Capture rationalizations from baseline testing (see Testing section below). Every excuse agents make goes in the table:

markdown

| Excuse | Reality |
|--------|---------|
| "Too simple to test" | Simple code breaks. Test takes 30 seconds. |
| "I'll test after" | Tests passing immediately prove nothing. |
| "Tests after achieve same goals" | Tests-after = "what does this do?" Tests-first = "what should this do?" |

Create Red Flags List

Make it easy for agents to self-check when rationalizing:

markdown

## Red Flags - STOP and Start Over

- Code before test
- "I already manually tested it"
- "Tests after achieve the same purpose"
- "It's about spirit not ritual"
- "This is different because..."

**All of these mean: Delete code. Start over with TDD.**

Update CSO for Violation Symptoms

Update the description using

TRIGGER-01

and

TRIGGER-02

from the shared standard. Add symptoms of when you're ABOUT to violate the rule:

yaml

description: use when implementing any feature or bugfix, before writing implementation code

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.

Testing methodology: See @testing-skills-with-subagents.md for the complete testing methodology:

How to write pressure scenarios
Pressure types (time, sunk cost, authority, exhaustion)
Plugging holes systematically
Meta-testing techniques

Anti-Patterns

❌ Narrative Example

"In session 2025-10-03, we found empty projectDir caused..." Why bad: Too specific, not reusable

❌ Multi-Language Dilution

example-js.js, example-py.py, example-go.go Why bad: Mediocre quality, maintenance burden

❌ Code in Flowcharts

dot

step1 [label="import fs"];
step2 [label="read file"];

Why bad: Can't copy-paste, hard to read

❌ Generic Labels

helper1, helper2, step3, pattern4 Why bad: Labels should have semantic meaning

STOP: Before Moving to Next Skill

After writing ANY skill, you MUST STOP and complete the deployment process.

Do NOT:

Create multiple skills in batch without testing each
Move to next skill before current one is verified
Skip testing because "batching is more efficient"

The deployment checklist below is MANDATORY for EACH skill.

Deploying untested skills = deploying untested code. It's a violation of quality standards.

Skill Creation Checklist (TDD Adapted)

IMPORTANT: Use TodoWrite to create todos for EACH checklist item below.

RED Phase - Write Failing Test:

Create pressure scenarios (3+ combined pressures for discipline skills)
Run scenarios WITHOUT skill - document baseline behavior verbatim
Identify patterns in rationalizations/failures

GREEN Phase - Write Minimal Skill:

Apply
```
NAME-01
```
and
```
FRONTMATTER-01
```
Apply
```
TRIGGER-01
```
,
```
TRIGGER-02
```
, and
```
SEARCH-01
```
Clear overview with core principle
Address specific baseline failures identified in RED
Apply
```
STRUCTURE-01
```
,
```
STRUCTURE-02
```
, and
```
DISCLOSURE-01
```
Apply
```
EXAMPLE-01
```
and
```
METADATA-01
```
where relevant
Run scenarios WITH skill - verify agents now comply

REFACTOR Phase - Close Loopholes:

Identify NEW rationalizations from testing
Add explicit counters (if discipline skill)
Build rationalization table from all test iterations
Create red flags list
Re-test until bulletproof

Quality Checks:

Shared-standard rules are satisfied without duplicating policy prose locally
Quick reference table or equivalent scan-friendly structure
Common mistakes or failure modes are easy to find
No narrative storytelling
Supporting files satisfy
```
TOPOLOGY-01
```
and
```
TOPOLOGY-02
```

Deployment:

Commit skill to git and push to your fork (if configured)
Consider contributing back via PR (if broadly useful)

The Bottom Line

Creating skills IS TDD for process documentation.

Same Iron Law: No skill without failing test first. Same cycle: RED (baseline) → GREEN (write skill) → REFACTOR (close loopholes). Same benefits: Better quality, fewer surprises, bulletproof results.

If you follow TDD for code, follow it for skills. It's the same discipline applied to documentation.

writing-skills

NPX Install

SKILL.md Content

Writing Skills

Overview

What is a Skill?

TDD Mapping for Skills

When to Create a Skill

Skill Types

Technique

Pattern

Reference

Authoring Standard

Optional Authoring Patterns

The Iron Law (Same as TDD)

Testing All Skill Types

Discipline-Enforcing Skills (rules/requirements)

Technique Skills (how-to guides)

Pattern Skills (mental models)

Reference Skills (documentation/APIs)

Common Rationalizations for Skipping Testing

Bulletproofing Skills Against Rationalization

Close Every Loophole Explicitly

Build Rationalization Table

Create Red Flags List

Update CSO for Violation Symptoms

RED-GREEN-REFACTOR for Skills

RED: Write Failing Test (Baseline)

GREEN: Write Minimal Skill

REFACTOR: Close Loopholes

Anti-Patterns

❌ Narrative Example

❌ Multi-Language Dilution

❌ Code in Flowcharts

❌ Generic Labels

STOP: Before Moving to Next Skill

Skill Creation Checklist (TDD Adapted)

The Bottom Line