pb-writing-skills

name	pb-writing-skills
description	Use when creating new skills, editing existing skills, or verifying skills work before deployment

pb-writing-skills

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

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

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

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)

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

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)

SKILL.md Structure

Frontmatter (YAML):

• Two required fields: name and description
• Max 1024 characters total
• name: Use letters, numbers, and hyphens only
• 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

---
name: Skill-Name-With-Hyphens
description: Use when [specific triggering conditions and symptoms]
---

# Skill Name

## Overview

What is this? Core principle in 1-2 sentences.

## When to Use

Bullet list with SYMPTOMS and use cases
When NOT to use

## Core Pattern (for techniques/patterns)

Before/after code comparison

## Quick Reference

Table or bullets for scanning common operations

## Implementation

Inline code for simple patterns

## Common Mistakes

What goes wrong + fixes

Skill Discovery Optimization (SDO)

Critical for discovery: Future agents need to FIND your skill

1. Rich Description Field

Your agent reads the description to decide which skills to load. 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

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.

# BAD: Summarizes workflow - agents may follow this instead of reading skill
description: Use when executing plans - dispatches subagent per task with code review between tasks

# GOOD: Just triggering conditions, no workflow summary
description: Use when executing implementation plans with independent tasks in the current session

Content:

• Use concrete triggers, symptoms, and situations that signal this skill applies
• Describe the problem not language-specific symptoms
• Keep triggers technology-agnostic unless the skill itself is technology-specific
• 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: 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:

# BAD: Document all flags in SKILL.md
search-conversations supports --text, --both, --after DATE, --before DATE, --limit N

# GOOD: Reference --help
search-conversations supports multiple modes and filters. Run --help for details.

Use cross-references:

# BAD: Repeat workflow details

When searching, dispatch subagent with template...
[20 lines of repeated instructions]

## GOOD: Reference other skill

Always use subagents (50-100x context savings). REQUIRED: Use [other-skill-name] for workflow.

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

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	Prohibition + rationalization table + red flags	Soft guidance ("prefer...", "consider...")
Complies, but output has the wrong shape	Positive recipe or contract: state what the output IS	Prohibition list ("don't restate", "never narrate")
Omits a required element from something they already produce	Structural: REQUIRED field or slot in the template	Prose reminders near the template
Behavior should depend on a condition	Conditional keyed to an observable predicate	Unconditional rule + exemption clauses

Rules for whichever form you pick:

• No nuance clauses. "Don't X unless it matters" reopens the negotiation.
• Exemption clauses don't scope. "This limit doesn't apply to code blocks" still suppresses code blocks.

Bulletproofing Skills Against Rationalization

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

Close Every Loophole Explicitly

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

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

Address "Spirit vs Letter" Arguments

Add foundational principle early:

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

Build Rationalization Table

Capture rationalizations from baseline testing. Every excuse agents make goes in the table:

| 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:

## 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.**

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?

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 guidance lands, reps converge on the same shape. Five different interpretations across five reps means the wording isn't binding — tighten the form before adding words.

Micro-tests verify wording; they do not replace pressure scenarios for discipline skills.

Testing All Skill Types

Discipline-Enforcing Skills (rules/requirements)

Test with:

• Academic questions: Do they understand the rules?
• Pressure scenarios: Do they comply under stress?
• Multiple pressures combined: time + sunk cost + exhaustion

Success criteria: Agent follows rule under maximum pressure

Technique Skills (how-to guides)

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)

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

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

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

Skill Creation Checklist (TDD Adapted)

IMPORTANT: Create a todo for EACH checklist item. Deploy each skill before starting the next.

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:

• Name uses only letters, numbers, hyphens
• YAML frontmatter with required name and description fields
• Description starts with "Use when..." and includes specific triggers/symptoms
• Description written in third person
• Keywords throughout for search (errors, symptoms, tools)
• Clear overview with core principle
• Address specific baseline failures identified in RED
• Guidance form matches the failure type (see Match the Form to the Failure)
• Code inline OR link to separate file
• One excellent example (not multi-language)
• 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:

• Quick reference table
• Common mistakes section
• No narrative storytelling
• Supporting files only for tools or heavy reference

Editing Existing Skills

Rules for Modification

1. Understand before changing — read the entire skill and its rationale
2. Preserve carefully-tuned content — Red Flags tables, rationalization lists, discipline patterns
3. Test changes — run the skill in a real session before committing
4. Document why — explain what problem the change solves

What NOT to Change

• Red Flags tables (anti-rationalization patterns)
• "Iron Law" sections (non-negotiable rules)
• Skill trigger conditions (unless adding new triggers)
• Integration points with other skills

Integration with pb-spec

• New pb-spec skills: Use this to create new workflow skills
• Skill maintenance: Use when updating existing skills
• Quality assurance: Use to verify skill behavior before release