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Official agent skill

Skill Builder

by block in block/berd

Create, edit, or inspect Berd skills stored as skill folders with SKILL.md files.

OfficialApache-2.0Auto-check passedAgent Workflows

Install Skill Builder

skills CLI
$ npx skills add block/berd --skill skill-builder -a claude-code

Project install by default; add -g for ~/.claude/skills/.

GitHub CLI
$ gh skill install block/berd skill-builder --agent claude-code

Project scope by default; add --scope user for a personal install. Needs GitHub CLI 2.90.0 or later (public preview).

Manual copy
$ git clone --depth 1 https://github.com/block/berd.git skills-src && mkdir -p .claude/skills && cp -r skills-src/distro/skills/skill-builder .claude/skills/skill-builder && rm -rf skills-src

Use ~/.claude/skills/ instead of .claude/skills for a personal install. The folder must contain SKILL.md.

Claude Code skills documentation · loads skills from .claude/skills/

Facts

Skill name
skill-builder
GitHub stars
969
Token cost
~1.2k tokens
SKILL.md length
581 words
Files
1
Skills in repo
11
Repo updated
First seen
Licence
Apache-2.0

At a glance

Create, edit, or inspect Berd skills stored as skill folders with SKILL.md files.

  • Works in 5 steps: Understand the skill with concrete… → Decide the skill shape. → Create or edit the skill folder. → …
  • The user wants to build a new skill
  • SKILL.md covers What a Skill Is, Storage Decision, Format and Names, plus 4 more sections
  • Instructions only: no scripts, shell commands, URLs or credentials in SKILL.md

What it does

Skill Builder is an agent skill from block/berd, published by the product's own GitHub organization. Create, edit, or inspect Berd skills stored as skill folders with SKILL.md files. Use when the user wants to build a new skill, update an existing skill, convert a workflow into a reusable skill, or decide whether instructions, scripts, references, or assets belong in a skill.

Its SKILL.md is about 1.2k tokens, which your agent loads only when the skill is triggered. It is a single SKILL.md file with no bundled scripts.

It sits in Agent Workflows, covering Skill authoring. The repository describes itself as: a desktop app for getting work done with any model. The licence is Apache-2.0.

When your agent uses it

  • The user wants to build a new skill
  • Update an existing skill
  • Convert a workflow into a reusable skill
  • Decide whether instructions

Example prompts

  • “/skill-builder”

Workflow steps

5 steps, taken from the first numbered list in SKILL.md.

  1. Understand the skill with concrete examples.
  2. Decide the skill shape.
  3. Create or edit the skill folder.
  4. Validate the result.
  5. Report the final path and a short summary of what the skill now does.

What it can do on your machine

Read from SKILL.md and the folder at commit bbdb311. It shows what the files ask for, not the result of running them.

  • Tool permissions

    Pre-approves nothing: there is no allowed-tools line, so your agent's usual permission prompts apply.

    From allowed-tools in the SKILL.md frontmatter.

  • Runs code

    No scripts in the folder and no shell commands in SKILL.md (its code samples are markdown).

    From the folder's file list and the shell code blocks in SKILL.md.

  • Network

    No URLs in SKILL.md.

    From URLs in SKILL.md, links to its own repository left out.

  • Credentials

    Names no API keys, tokens, secrets or passwords.

    From names ending in _API_KEY, _TOKEN, _SECRET, _KEY or _PASSWORD in SKILL.md.

Context cost

Skill Builder loads about 1.2k tokens when it runs. Until then it costs about 73 tokens; SKILL.md has 581 words of instructions outside code blocks.

Always · name and description, kept in context so the agent knows when to use it
~73
When it runs · the whole SKILL.md, loaded when a task matches
~1.2k

Estimates: characters ÷ 4, the usual rule of thumb; real counts depend on the model's tokenizer. Scripts and assets cost tokens only if the agent reads them.

Safety

Auto-check passed

The automated check found no risky patterns in SKILL.md.

Automated static check — not a guarantee. Review scripts before installing. It scans the text of SKILL.md for risky patterns (piping downloads into a shell, reading credential files, hidden Unicode, destructive commands); files beside SKILL.md are not scanned.

SKILL.md

The full file from block/berd at commit bbdb311, republished under its Apache-2.0 licence (© block). 581 words, ~1,158 tokens.

Download SKILL.mdSave it as .claude/skills/skill-builder/SKILL.md (or your agent's skills folder).
name
skill-builder
description
Create, edit, or inspect Berd skills stored as skill folders with SKILL.md files. Use when the user wants to build a new skill, update an existing skill, convert a workflow into a reusable skill, or decide whether instructions, scripts, references, or assets belong in a skill.
metadata.berdBundled
true

Skill Builder

Use this skill when creating, editing, or inspecting Berd skills.

What a Skill Is

A skill is a folder with a required SKILL.md file and optional supporting resources:

text
skill-name/
├── SKILL.md
├── scripts/
├── references/
└── assets/

Do not create README.md, CHANGELOG.md, or extra documentation files inside a skill folder. Skill documentation belongs in SKILL.md or references/.

Storage Decision

Skills can be global or project-local:

  • Global: ~/.agents/skills/<skill-name>/SKILL.md
  • Project-local: <project>/.agents/skills/<skill-name>/SKILL.md

Default to global unless the user is clearly working in a project directory.

If a project directory is active and the user has not specified scope, ask whether the skill should be saved for this project only or globally for all projects.

Do not ask when intent is clear:

  • Project-local: "this repo", "this project", "only here", "project skill"
  • Global: "all projects", "global", "personal skill", "always available"

When editing an existing skill, keep it in its current location unless the user explicitly asks to move it.

Format

SKILL.md is UTF-8 Markdown with YAML frontmatter:

md
---
name: skill-name
description: What the skill does. Use when the user asks to...
---

# Skill Title

Instructions the agent follows.

Required frontmatter keys are name and description. Preserve unknown frontmatter keys when editing existing skills unless the user explicitly asks to change them.

The description is the trigger surface. It must explain both what the skill does and when to use it. Include concrete user phrases or task types. Keep it specific enough to avoid triggering for unrelated work.

Names

Skill names and folder names must match.

Use lowercase kebab-case:

  • Allowed: a-z, 0-9, and -
  • Maximum: 64 characters
  • Do not start or end with -
  • Do not use spaces, underscores, slashes, or capitals

Normalize user-provided titles by lowercasing, replacing invalid character runs with -, collapsing repeated separators when practical, trimming leading and trailing -, and truncating to 64 characters. Fall back to skill if needed.

On create collisions, use <skill-name>-2, <skill-name>-3, etc.

Show full SKILL.md (298 more words)Show less

Authoring Workflow

  1. Understand the skill with concrete examples. Ask for 2-3 example requests or workflows if the goal is vague. Do not ask when the user has already provided enough detail.
  2. Decide the skill shape. Keep simple procedural guidance in SKILL.md. Add optional folders only when they earn their keep:
    • scripts/ for deterministic or repeatedly rewritten code
    • references/ for detailed docs loaded only when needed
    • assets/ for templates, fonts, icons, or files used in outputs
  3. Create or edit the skill folder. Prefer direct file edits over helper scripts unless the repo already has a relevant script.
  4. Validate the result. Confirm the folder exists, SKILL.md exists with exact casing, frontmatter is valid YAML, required keys are present, the name matches the folder, and existing metadata was preserved.
  5. Report the final path and a short summary of what the skill now does.

Editing Existing Skills

Read the existing skill before editing. Resolve targets by exact path, then frontmatter name, then folder name. Ask only if multiple matches remain.

Preserve supporting folders and unknown files unless the user explicitly asks to remove them.

Quality Checklist

Before finishing, check:

  • The skill has a clear, narrow purpose.
  • The description has likely trigger phrases and avoids vague claims.
  • Critical instructions are near the top of the body.
  • The body is concise; detailed material moves to references/.
  • Any fragile or repetitive operation uses a script where practical.
  • The skill can work alongside other skills without assuming it is the only active skill.

Trigger Testing

When useful, suggest a tiny test set:

  • Should trigger: obvious requests and paraphrases for the workflow.
  • Should not trigger: unrelated tasks and adjacent workflows outside scope.

If a skill under-triggers, make the description more concrete. If it over-triggers, narrow the description and add negative scope guidance.

© block, Apache-2.0. Rendered from Markdown: HTML in the file is shown as text, images as links, and headings moved down two levels. Raw file

Files

Just SKILL.md in distro/skills/skill-builder of block/berd.

Open the folder on GitHubat commit bbdb311

Compare with similar skills

Skill Builder next to the 5 skills that share the most tags, products or categories with it. Stars are the repository's; “used in” counts other GitHub owners with a copy.

Skill Builder compared with similar skills
SkillStarsUsed inTokensAuto-checkLicenceRepo updated
Skill Builder this skillblock/berd969—~1.2kAutomated safety check: PassApache-2.0
Skill CreatorAzure/azqr79489 repos~8.2kAutomated safety check: PassApache-2.0
Claude Code Skill Developer Guidediet103/claude-code-infrastructure-showcase10k10 repos~3.5kAutomated safety check: PassMIT
Darwin Skill Optimizeralchaincyf/darwin-skill6.2k1 repos~4.7kAutomated safety check: PassMIT
Claude Code Command Developmentanthropics/claude-plugins-official37k10 repos~4.8kAutomated safety check: PassApache-2.0
Claude Code Plugin Structureanthropics/claude-plugins-official37k10 repos~3.4kAutomated safety check: PassApache-2.0

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Categories

Questions about Skill Builder

What does Skill Builder do?

Create, edit, or inspect Berd skills stored as skill folders with SKILL.md files. Skill Builder is an agent skill from block/berd, published by the product's own GitHub organization.md files.

When should I use Skill Builder?

Skill Builder fits situations like: the user wants to build a new skill; update an existing skill; convert a workflow into a reusable skill; decide whether instructions.

How do I install Skill Builder in Claude Code?

Run `npx skills add block/berd --skill skill-builder -a claude-code`. Or copy the skill folder (distro/skills/skill-builder in block/berd) into .claude/skills/skill-builder in your project. Claude Code loads it when a task matches its description.

How do I install Skill Builder in Codex?

Run `npx skills add block/berd --skill skill-builder -a codex`. Or copy the skill folder (distro/skills/skill-builder in block/berd) into .agents/skills/skill-builder in your project. Codex loads it when a task matches its description.

Can I use Skill Builder in Cursor, Gemini CLI or GitHub Copilot?

Cursor, Gemini CLI, GitHub Copilot and OpenCode also load SKILL.md folders. With the skills CLI, run `npx skills add block/berd --skill skill-builder -a cursor` (or -a gemini-cli, github-copilot or opencode for the others). To copy it by hand, put the folder in .cursor/skills/skill-builder, .gemini/skills/skill-builder, .github/skills/skill-builder and .opencode/skills/skill-builder in your project.

What does Skill Builder need to run?

SKILL.md names no scripts, command-line tools or credentials: Skill Builder is instructions for the agent only.

Does Skill Builder access the network?

SKILL.md contains no URLs. Any network use would come from the scripts or tools the agent runs. This is read from the text; nothing was executed.

Is Skill Builder safe to install?

Our automated static check of SKILL.md found no risky patterns, such as piping downloads into a shell, reading credential files or hidden Unicode. It is not a guarantee. Review the folder before installing.

What licence does Skill Builder use?

Skill Builder is published under the Apache-2.0 licence (the repository's licence). It allows redistribution, so the full SKILL.md is shown on this page.

How many tokens does Skill Builder use?

About 1.2k tokens (SKILL.md is roughly 4.6k characters). Agents keep only the skill's name and description in context until a task matches; then they load SKILL.md in full.

What are the alternatives to Skill Builder?

Skills that share tags, products or a category with Skill Builder: Skill Creator (Azure/azqr, 794 stars), Claude Code Skill Developer Guide (diet103/claude-code-infrastructure-showcase, 10k stars), Darwin Skill Optimizer (alchaincyf/darwin-skill, 6.2k stars) and Claude Code Command Development (anthropics/claude-plugins-official, 37k stars). The comparison table on this page puts their stars, adoption, token cost, safety result and licence side by side.

Who maintains Skill Builder?

block (a GitHub organization, an official publisher) maintains it in block/berd, which has 969 GitHub stars. The repository holds 11 skills in this directory. The repository was last updated on October 6, 2026.

Source: block/berd on GitHub. Facts on this page come from the repository at the commit we read; the author's words are quoted as theirs.