Fastclaw Skill Guide

FastClaw Skill Guide

Guide for creating new skills that FastClaw agents can discover and use.

Skill Structure

skill-name/
├── SKILL.md          # Required — skill instructions
├── scripts/          # Optional — executable scripts for deterministic tasks
├── references/       # Optional — docs loaded into context as needed
└── assets/           # Optional — templates, icons, fonts

SKILL.md Format

Use YAML frontmatter followed by markdown instructions:

---
name: My Skill Name
description: One-line description of what this skill does and when to use it
homepage: https://example.com
metadata:
  fastclaw:
    emoji: "🔧"
    always: false
    os: ["darwin", "linux"]
    requires:
      bins: ["git"]
      anyBins: ["python3", "python"]
      env: ["API_KEY"]
    primaryEnv: "API_KEY"
---

# Skill Title

Step-by-step instructions in markdown...

Frontmatter Fields

Note: metadata.openclaw is also supported for backward compatibility with OpenClaw skills.

Writing the Description

The description determines whether the agent loads this skill. Make it specific and slightly "pushy" — include both what the skill does AND contexts where it should trigger.

Bad: "Format data" Good: "Format CSV and Excel data into clean tables. Use whenever the user mentions spreadsheets, data formatting, column alignment, CSV cleanup, or tabular output."

Where Skills Are Stored

Skills are discovered from multiple directories in precedence order (higher overrides lower):

1. Agent workspace — {agentDir}/skills/ — skills specific to this agent
2. Team — {teamDir}/skills/ — shared within a team
3. User installed — ~/.fastclaw/skills/ — user-level skills
4. OpenClaw compatible — ~/.openclaw/skills/ — installed via OpenClaw
5. System bundled — npm global locations
6. Extra dirs — configured in fastclaw.json

Three-Level Loading

Skills use progressive disclosure:

1. Metadata (name + description) — Always in system prompt context (~100 words)
2. SKILL.md body — Loaded when agent calls load_skill (<500 lines ideal)
3. Bundled resources — Loaded on demand via file tools (unlimited size)

Keep SKILL.md under 500 lines. If approaching the limit, move detailed content to references/ with clear pointers.

Writing Guidelines

• Use imperative form in instructions ("Run the command", not "You should run the command")
• Explain why things are important, not just what to do
• Include examples for output formats
• Use {baseDir} token to reference files within the skill directory — it gets replaced with the absolute path at load time
• Avoid heavy MUST/NEVER language — explain reasoning so the agent can handle edge cases

Creation Steps

1. Capture intent — What should this skill enable? When should it trigger?
2. Write SKILL.md — Frontmatter + step-by-step instructions
3. Add resources — Scripts in scripts/, docs in references/, templates in assets/
4. Save — Write to {agentDir}/skills/{skill-name}/SKILL.md for agent-level, or ~/.fastclaw/skills/{skill-name}/SKILL.md for user-level
5. Verify — Use load_skill tool to confirm it loads correctly

Example

---
name: git-pr-review
description: Review pull requests with structured feedback. Use when the user asks to review a PR, check code changes, or provide feedback on a merge request.
---

# PR Review

Review a pull request and provide structured feedback.

## Steps

1. Get the PR diff:
   ```bash
   git diff main...HEAD

2. For each changed file, check:

   • Code correctness and edge cases
   • Naming and readability
   • Test coverage

3. Output feedback in this format:

   Summary

   One-paragraph overview.

   Issues

   • file:line — description of issue

   Suggestions

   • Optional improvements