Getting it into your agent
One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.
npx skills add brain-bootstrap/claude-code-brain-bootstrap --skill writing-skillsgit clone --depth 1 https://github.com/brain-bootstrap/claude-code-brain-bootstrapWrote this? Show the measurements
A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.
[](https://agentmods.dev/skills/brain-bootstrap/claude-code-brain-bootstrap/writing-skills)<a href="https://agentmods.dev/skills/brain-bootstrap/claude-code-brain-bootstrap/writing-skills"><img src="https://agentmods.dev/badge/skills/brain-bootstrap/claude-code-brain-bootstrap/writing-skills/github.svg" alt="Measured on agentmods" height="20"></a>Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.
<a href="https://agentmods.dev/skills/brain-bootstrap/claude-code-brain-bootstrap/writing-skills"><img src="https://agentmods.dev/badge/skills/brain-bootstrap/claude-code-brain-bootstrap/writing-skills.svg" alt="Reviewed on agentmods" width="80" height="20"></a>What it costs to keep this loaded
Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.
| Model | Per session | Once invoked |
|---|---|---|
| Fable 5.1 | $0.00036 | $0.01190 |
| Opus 5.5 | $0.00014 | $0.00476 |
| Sonnet 5.5 | $0.00007 | $0.00238 |
| Haiku 4.5 | $0.00004 | $0.00119 |
Grade A, and why
writing-skills scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 1mo ago.
A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.
Nothing flagged
None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.
How it starts
The opening of the file, as written. The whole thing — 166 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Writing Skills
Overview
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, project-specific conventions (those go in CLAUDE.md)
SKILL.md Structure
Frontmatter (YAML):
- Required fields:
name,description - Max 1024 characters total
name: Letters, numbers, hyphens only — no parentheses or special charsdescription: Third-person, describes ONLY when to use (NOT what it does) — see CSO section
---
name: skill-name
description: Use when [specific triggering conditions and symptoms]
user-invocable: true # only if user should invoke with /skill-name
---
# Skill Name
## Overview
Core principle in 1-2 sentences.
## When to Use
Bullet list with symptoms and use cases. When NOT to use.
## Core Pattern
Before/after comparison or workflow steps.
## Quick Reference
Table or bullets for scanning.
## Common Mistakes
What goes wrong + fixes.
Claude Search Optimization (CSO)
The description field is the discovery mechanism. Claude reads it to decide which skills to load.
Description = Triggering Conditions ONLY
NEVER summarize the skill's workflow in the description.
Why this matters: Testing revealed that when a description summarizes the workflow, Claude follows the description instead of reading the full skill body. A description saying "code review between tasks" caused Claude to do ONE review, even though the skill's flowchart showed TWO reviews. Changing the description to triggering conditions only fixed it.
The trap: Descriptions that summarize workflow create a shortcut Claude will take. The skill body becomes documentation Claude skips.
# BAD: Summarizes workflow — Claude 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
description: Use when executing implementation plans with independent tasks in the current session
What this file has done since we first saw it
Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.
- 1mo ago First seen · 166 lines · 36 tokens per session scan A 561aa75b9ff2
writing-skills is a skill published in the GitHub repository brain-bootstrap/claude-code-brain-bootstrap (11 stars, last pushed 5mo ago), licensed MIT. It adds 36 tokens to every session and 1,190 once invoked, about $0.0001 per session on Opus 5.5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-09-03.
Other skills, from other repositories
implement
TRIGGER when: user asks to implement, fix, build, or work on something — whether from a docs/feat/wip plan OR a standalone task (bug fix, GitHub issue, one-off change). Examples: "work on task 1", "fix this bug", "implement feature X from the issue". Provides structured execution with profile detection, dependency…
review-spec
Use after implementing tasks or mid-feature to verify code matches design docs and ensure they are in sync. Detects spec deviations, missing implementations, doc inconsistencies, and outdated docs in design and implementation documentation.
chain-of-verification
Apply Chain-of-Verification (CoVe) prompting to improve response accuracy through self-verification. Use when complex questions require fact-checking, technical accuracy, or multi-step reasoning.
review-design
Review design, implementation, and task documents produced by design. Evaluates document quality, internal consistency, and technical soundness. Use after design completes and before starting implement.
review-architecture
Review a written architecture artifact — an ADR (docs/adr/), a broader architecture doc, the architecture section of a design doc, or a domain-reference kit (glossary + traps pages, reviewed as one composite artifact) — against the system it claims to describe. Verifies the EXISTENCE and TOPOLOGY of declared…
model
Produce or update a domain-reference kit — the durable glossary + divergences/traps pages for a bounded context. Use for domain modelling, information architecture, building a domain glossary or domain model, mapping domain concepts to code (bindings), or surfacing the decidable questions stakeholders must close…