Skill Writer

Write high-quality agent skills (SKILL.md files) for ClawdHub/MoltHub. Use when creating a new skill from scratch, structuring skill content, writing effective frontmatter and descriptions, choosing section patterns, or following best practices for agent-consumable technical documentation.

Security Scan

This is an instruction-only, meta skill that teaches how to write SKILL.md files; its requirements and behavior are coherent and there is no code or credential access requested.

Purpose & Capability

The skill's purpose is to author SKILL.md files and the SKILL.md content matches that purpose. The frontmatter in the skill declares an anyBins requirement for `npx` — mildly unexpected for a purely documentation skill but justifiable because the instructions reference running `npx molthub@latest search`. Requiring `npx` is optional for purely authoring work; it's not harmful but slightly broader than strictly necessary.

Instruction Scope

The SKILL.md instructions are limited to authoring guidance, formatting rules, examples, and occasional CLI examples (e.g., `npx molthub@latest search`). The instructions do not request reading system files, environment secrets, or transmitting user data to external endpoints.

Install Mechanism

No install spec is present (instruction-only). Nothing is downloaded or written to disk by the skill itself, which minimizes install-time risk.

Credentials

The skill declares no required environment variables or credentials and does not ask for access to config paths or secrets. The only runtime hint is an optional requirement for `npx` in metadata.

Persistence & Privilege

The skill is not forced-present (always: false) and does not request elevated system presence. Autonomous invocation is allowed (platform default) but the skill's instructions are benign and scoped to documentation tasks.

Assessment

This is a documentation-only skill for writing SKILL.md files and contains no code or credential requests — low risk. Note the metadata suggests `npx` as an available tool because examples use `npx molthub@latest search`; you don't need to install anything to read or use the guidance. Before publishing any SKILL.md you create, avoid embedding secrets or credentials in examples, run any CLI commands (like npx) yourself in a safe environment, and review the final frontmatter so it only lists tools the real skill actually needs.

Write well-structured, effective SKILL.md files for the ClawdHub registry. Covers the skill format specification, frontmatter schema, content patterns, example quality, and common anti-patterns.

When to Use

• Creating a new skill from scratch
• Structuring technical content as an agent skill
• Writing frontmatter that the registry indexes correctly
• Choosing section organization for different skill types
• Reviewing your own skill before publishing

The SKILL.md Format

A skill is a single Markdown file with YAML frontmatter. The agent loads it on demand and follows its instructions.

---
name: my-skill-slug
description: One-sentence description of when to use this skill.
metadata: {"clawdbot":{"emoji":"🔧","requires":{"anyBins":["tool1","tool2"]},"os":["linux","darwin","win32"]}}
---

# Skill Title

One-paragraph summary of what this skill covers.

## When to Use

- Bullet list of trigger scenarios

## Main Content Sections

### Subsection with examples

Code blocks, commands, patterns...

## Tips

- Practical advice bullets

Frontmatter Schema

name (required)

The skill's slug identifier. Must match what you publish with.

name: my-skill

Rules:

• Lowercase, hyphenated: csv-pipeline, git-workflows
• No spaces, no underscores
• Keep it short and descriptive (1-3 words)
• Check for slug collisions before publishing: npx molthub@latest search "your-slug"

description (required)

The single most important field. This is what:

1. The registry indexes for semantic search (vector embeddings)
2. The agent reads to decide whether to activate the skill
3. Users see when browsing search results

# GOOD: Specific triggers and scope
description: Write Makefiles for any project type. Use when setting up build automation, defining multi-target builds, managing dependencies between tasks, creating project task runners, or using Make for non-C projects (Go, Python, Docker, Node.js). Also covers Just and Task as modern alternatives.

# BAD: Vague, no triggers
description: A skill about Makefiles.

# BAD: Too long (gets truncated in search results)
description: This skill covers everything you need to know about Makefiles including variables, targets, prerequisites, pattern rules, automatic variables, phony targets, conditional logic, multi-directory builds, includes, silent execution, and also covers Just and Task as modern alternatives to Make for projects that use Go, Python, Docker, or Node.js...

Pattern for effective descriptions:

[What it does]. Use when [trigger 1], [trigger 2], [trigger 3]. Also covers [related topic].

metadata (required)

JSON object with the clawdbot schema:

metadata: {"clawdbot":{"emoji":"🔧","requires":{"anyBins":["make","just"]},"os":["linux","darwin","win32"]}}

Fields:

• emoji: Single emoji displayed in registry listings
• requires.anyBins: Array of CLI tools the skill needs (at least one must be available)
• os: Array of supported platforms: "linux", "darwin" (macOS), "win32" (Windows)

Choose requires.anyBins carefully:

# Good: lists the actual tools the skill's commands use
"requires": {"anyBins": ["docker", "docker-compose"]}

# Bad: lists generic tools every system has
"requires": {"anyBins": ["bash", "echo"]}

# Good for skills that work via multiple tools
"requires": {"anyBins": ["make", "just", "task"]}

Content Structure

The "When to Use" Section

Always include this immediately after the title paragraph. It tells the agent (and the user) the specific scenarios where this skill applies.

## When to Use

- Automating build, test, lint, deploy commands
- Defining dependencies between tasks (build before test)
- Creating a project-level task runner
- Replacing long CLI commands with short targets

Rules:

• 4-8 bullet points
• Each bullet is a concrete scenario, not an abstract concept
• Start with a verb or gerund: "Automating...", "Debugging...", "Converting..."
• Don't repeat the description field verbatim

Main Content Sections

Organize by task, not by concept. The agent needs to find the right command for a specific situation.

## GOOD: Organized by task
## Encode and Decode
### Base64
### URL Encoding
### Hex

## BAD: Organized by abstraction
## Theory of Encoding
## Encoding Types
## Advanced Topics

Code Blocks

Every section should have at least one code block. Skills without code blocks are opinions, not tools.

## GOOD: Concrete, runnable example
```bash
# Encode a string to Base64
echo -n "Hello, World!" | base64
# SGVsbG8sIFdvcmxkIQ==
```

## BAD: Abstract description
Base64 encoding converts binary data to ASCII text using a 64-character alphabet...

Code block best practices:

• Always specify the language (bash, python, javascript, yaml, sql, etc.)
• Show the output in a comment below the command
• Use realistic values, not foo/bar (use myapp, api-server, real IP formats)
• Include the most common case first, then variations
• Add inline comments for non-obvious flags or arguments

Multi-Language Coverage

If a skill applies across languages, use consistent section structure:

## Hashing

### Bash
```bash
echo -n "Hello" | sha256sum

JavaScript

const crypto = require('crypto');
crypto.createHash('sha256').update('Hello').digest('hex');

Python

import hashlib
hashlib.sha256(b"Hello").hexdigest()

Order: Bash first (most universal), then by popularity for the topic.

### The "Tips" Section

End every skill with a Tips section. These are the distilled wisdom — the things that save hours of debugging.

```markdown
## Tips

- The number one Makefile bug: using spaces instead of tabs for indentation.
- SHA-256 is the standard for integrity checks. MD5 is fine for dedup but broken for cryptographic use.
- Never schedule critical cron jobs between 1:00-3:00 AM if DST applies.

Rules:

• 5-10 bullets
• Each tip is a standalone insight (no dependencies on other tips)
• Prioritize gotchas and non-obvious behavior over basic advice
• No "always use best practices" platitudes

Skill Types and Templates

CLI Tool Reference

For skills about a specific tool or command family.

---
name: tool-name
description: [What tool does]. Use when [scenario 1], [scenario 2].
metadata: {"clawdbot":{"emoji":"🔧","requires":{"anyBins":["tool-name"]}}}
---

# Tool Name

[One paragraph: what it does and why you'd use it.]

## When to Use
- [4-6 scenarios]

## Quick Reference
[Most common commands with examples]

## Common Operations
### [Operation 1]
### [Operation 2]

## Advanced Patterns
### [Pattern 1]

## Troubleshooting
### [Common error and fix]

## Tips

Language/Framework Reference

For skills about patterns in a specific language or framework.

---
name: pattern-name
description: [Pattern] in [language/framework]. Use when [scenario 1], [scenario 2].
metadata: {"clawdbot":{"emoji":"📐","requires":{"anyBins":["runtime"]}}}
---

# Pattern Name

## When to Use

## Quick Reference
[Cheat sheet / syntax summary]

## Patterns
### [Pattern 1 — with full example]
### [Pattern 2 — with full example]

## Cross-Language Comparison (if applicable)

## Anti-Patterns
[What NOT to do, with explanation]

## Tips

Workflow/Process Guide

For skills about multi-step processes.

---
name: workflow-name
description: [Workflow description]. Use when [scenario 1], [scenario 2].
metadata: {"clawdbot":{"emoji":"🔄","requires":{"anyBins":["tool1","tool2"]}}}
---

# Workflow Name

## When to Use

## Prerequisites
[What needs to be set up first]

## Step-by-Step
### Step 1: [Action]
### Step 2: [Action]
### Step 3: [Action]

## Variations
### [Variation for different context]

## Troubleshooting

## Tips

Anti-Patterns

Too abstract

# BAD
## Error Handling
Error handling is important for robust applications. You should always
handle errors properly to prevent unexpected crashes...

# GOOD
## Error Handling
```bash
# Bash: exit on any error
set -euo pipefail

# Trap for cleanup on exit
trap 'rm -f "$TMPFILE"' EXIT

### Too narrow

```markdown
# BAD: Only useful for one specific case
---
name: react-useeffect-cleanup
description: How to clean up useEffect hooks in React
---

# GOOD: Broad enough to be a real reference
---
name: react-hooks
description: React hooks patterns. Use when working with useState, useEffect, useCallback, useMemo, custom hooks, or debugging hook-related issues.
---

Wall of text without examples

If any section goes more than 10 lines without a code block, it's too text-heavy. Break it up with examples.

Missing cross-references

If your skill mentions another tool or concept that has its own skill, note it:

# For Docker networking issues, see the `container-debug` skill.
# For regex syntax details, see the `regex-patterns` skill.

Outdated commands

Verify every command works on current tool versions. Common traps:

• Docker Compose: docker-compose (v1) vs. docker compose (v2)
• Python: pip vs. pip3, python vs. python3
• Node.js: CommonJS (require) vs. ESM (import)

Size Guidelines

Metric	Target	Too Short	Too Long
Total lines	300-550	< 150	> 700
Sections	5-10	< 3	> 15
Code blocks	15-40	< 8	> 60
Tips	5-10	< 3	> 15

A skill under 150 lines probably lacks examples. A skill over 700 lines should be split into two skills.

Publishing Checklist

Before publishing, verify:

1. Frontmatter is valid YAML — test by pasting into a YAML validator
2. Description starts with what the skill does — not "This skill..." or "A skill for..."
3. Every section has at least one code block — no text-only sections in the main content
4. Commands actually work — test in a clean environment
5. No placeholder values left — search for TODO, FIXME, example.com used as real URLs
6. Slug is available — npx molthub@latest search "your-slug" returns no exact match
7. requires.anyBins lists real dependencies — tools the skill's commands actually invoke
8. Tips section exists — with 5+ actionable, non-obvious bullets

Publishing

# Publish a new skill
npx molthub@latest publish ./skills/my-skill \
  --slug my-skill \
  --name "My Skill" \
  --version 1.0.0 \
  --changelog "Initial release"

# Update an existing skill
npx molthub@latest publish ./skills/my-skill \
  --slug my-skill \
  --name "My Skill" \
  --version 1.1.0 \
  --changelog "Added new section on X"

# Verify it's published
npx molthub@latest search "my-skill"

Tips

• The description field is your skill's search ranking. Spend more time on it than any single content section. Include the specific verbs and nouns users would search for.
• Lead with the most common use case. If 80% of users need "how to encode Base64", put that before "how to convert between MessagePack and CBOR."
• Every code example should be copy-pasteable. If it needs setup that isn't shown, add the setup.
• Write for the agent, not the human. The agent needs unambiguous instructions it can follow step by step. Avoid "you might want to consider" — say "do X when Y."
• Test your skill by asking an agent to use it on a real task. If the agent can't follow the instructions to produce a correct result, the skill needs work.
• Prefer bash code blocks for commands, even in language-specific skills. The agent often operates via shell, and bash blocks signal "run this."
• Don't duplicate what --help already provides. Focus on patterns, combinations, and the non-obvious things that --help doesn't teach.
• Version your skills semantically: patch for typo fixes, minor for new sections, major for restructures. The registry tracks version history.