Agent skill

Building Skills

by aiskillstore in aiskillstore/marketplace

Expert at creating and modifying Claude Code skills. An agent skill from aiskillstore/marketplace.

No licenceAuto-check: notes

Install Building Skills

skills CLI
$ npx skills add aiskillstore/marketplace --skill building-skills -a claude-code

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

GitHub CLI
$ gh skill install aiskillstore/marketplace building-skills --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/aiskillstore/marketplace.git skills-src && mkdir -p .claude/skills && cp -r skills-src/skills/c0ntr0lledcha0s/building-skills .claude/skills/building-skills && 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
building-skills
GitHub stars
433
Token cost
~4k tokens
SKILL.md length
1,226 words
Files
5 (incl. scripts, references)
Skills in repo
1,044
Repo updated
First seen
Licence
None found

At a glance

Expert at creating and modifying Claude Code skills. An agent skill from aiskillstore/marketplace.

  • Works in 7 steps: Gather Requirements → Design the Skill → Create the Directory Structure → …
  • Wants to create
  • SKILL.md covers When to Create a Skill vs…, Key Differences: Skills vs…, Skill Schema & Structure and Skill Body Content, plus 7 more sections
  • Runs Python scripts from its folder; calls python3

What it does

Building Skills is an agent skill from aiskillstore/marketplace. Expert at creating and modifying Claude Code skills. Auto-invokes when the user wants to create, update, modify, enhance, validate, or standardize skills, or when modifying skill YAML frontmatter fields (especially 'allowed-tools', 'description'), needs help designing skill architecture, or wants to understand when to use skills vs agents. Also auto-invokes proactively when Claude is about to write skill files (/skills//SKILL.md), create skill directory structures, or implement tasks that involve creating skill…

Its SKILL.md is about 4k tokens, which your agent loads only when the skill is triggered. The skill folder holds 7 other files, including scripts and reference files (for example `references/skill-maintenance-guide.md`, `scripts/validate-skill.py` and `skill-report.json`).

The repository describes itself as: Security-audited skills for Claude, Codex & Claude Code. One-click install, quality verified.

When your agent uses it

  • Wants to create
  • Standardize skills
  • Modifying skill YAML frontmatter fields (especially allowed-tools
  • Needs help designing skill architecture

Example prompts

  • “allowed-tools”
  • “description”
  • “/building-skills”

Requirements

  • Python 3
  • Pre-approved tools (allowed-tools): Read, Write, Edit, Grep, Glob, Bash

Workflow steps

7 steps, taken from the step headings in SKILL.md.

  1. Gather Requirements
  2. Design the Skill
  3. Create the Directory Structure
  4. Write SKILL.md
  5. Add Resources
  6. Validate the Skill
  7. Test the Skill

What it can do on your machine

Read from SKILL.md and the folder at commit 44923f3. It shows what the files ask for, not the result of running them.

  • Tool permissions

    Pre-approves these tools, so the agent can use them without asking each time:

    • Read
    • Write
    • Edit
    • Grep
    • Glob
    • Bash

    From allowed-tools in the SKILL.md frontmatter.

  • Runs code

    Ships 1 file in scripts/ (Python), which the agent can run.

    Shell commands in SKILL.md call:

    • python3

    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

Building Skills loads about 4k tokens when it runs, and up to ~5.6k if it reads all its reference files. Until then it costs about 137 tokens; SKILL.md has 1,226 words of instructions outside code blocks.

Always · name and description, kept in context so the agent knows when to use it
~137
When it runs · the whole SKILL.md, loaded when a task matches
~4k
With references · SKILL.md plus every file in references/, read only if the agent opens them
~5.6k

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: notes

The automated check noted patterns worth knowing about, such as sudo or a known installer.

  • NotePre-approves every shell command (allowed-tools: Bash)SKILL.md
    allowed-tools: Read, Write, Edit, Grep, Glob, Bash

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); the scripts in this folder are not scanned.

SKILL.md

Without a licence we can't republish the file, so here is its outline and opening line. It has 1,226 words (~4,036 tokens).

“You are an expert at creating Claude Code skills. Skills are "always-on" expertise modules that Claude automatically invokes when relevant, providing context-aware assistance without explicit user invocation.”

— opening of SKILL.md by aiskillstore
name
building-skills
allowed-tools
Read, Write, Edit, Grep, Glob, Bash
version
2.0.0

Read the full SKILL.md on GitHub

Files

SKILL.md and 4 other files (scripts, references) in skills/c0ntr0lledcha0s/building-skills of aiskillstore/marketplace.

  • SKILL.md
  • references/skill-maintenance-guide.md
  • scripts/validate-skill.py
  • skill-report.json
  • templates/skill-template.md

Open the folder on GitHubat commit 44923f3

Compare with similar skills

Building Skills 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.

Building Skills compared with similar skills
SkillStarsUsed inTokensAuto-checkLicenceRepo updated
Building Skills this skillaiskillstore/marketplace433—~4kAutomated safety check: NotesNone
Gameobject ModifyIvanMurzak/Unity-MCP4.4k—~2.3kAutomated safety check: PassApache-2.0
Object ModifyIvanMurzak/Unity-MCP4.4k—~2.3kAutomated safety check: PassApache-2.0
Assets ModifyIvanMurzak/Unity-MCP4.4k—~1.7kAutomated safety check: PassApache-2.0
Modifying Taxonomic FilterPostHog/posthog40k—~2.8kAutomated safety check: PassCustom licence
Migrating To Modifier NoderosuH/EasyWatermark1.9k1 repos~5kAutomated safety check: PassApache-2.0

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Questions about Building Skills

What does Building Skills do?

Expert at creating and modifying Claude Code skills. An agent skill from aiskillstore/marketplace. Building Skills is an agent skill from aiskillstore/marketplace. Expert at creating and modifying Claude Code skills.

When should I use Building Skills?

Building Skills fits situations like: wants to create; standardize skills; modifying skill YAML frontmatter fields (especially allowed-tools; needs help designing skill architecture.

How do I install Building Skills in Claude Code?

Run `npx skills add aiskillstore/marketplace --skill building-skills -a claude-code`. Or copy the skill folder (skills/c0ntr0lledcha0s/building-skills in aiskillstore/marketplace) into .claude/skills/building-skills in your project. Claude Code loads it when a task matches its description.

How do I install Building Skills in Codex?

Run `npx skills add aiskillstore/marketplace --skill building-skills -a codex`. Or copy the skill folder (skills/c0ntr0lledcha0s/building-skills in aiskillstore/marketplace) into .agents/skills/building-skills in your project. Codex loads it when a task matches its description.

Can I use Building Skills 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 aiskillstore/marketplace --skill building-skills -a cursor` (or -a gemini-cli, github-copilot or opencode for the others). To copy it by hand, put the folder in .cursor/skills/building-skills, .gemini/skills/building-skills, .github/skills/building-skills and .opencode/skills/building-skills in your project.

What does Building Skills need to run?

Going by SKILL.md and its folder, Building Skills needs Python for the scripts in its folder and the command-line tools its instructions call (python3). Our summary lists: Python 3. Its frontmatter pre-approves these tools: Read, Write, Edit, Grep, Glob, Bash.

Does Building Skills 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 Building Skills safe to install?

Our automated static check of SKILL.md found notes only (pre-approves every shell command (allowed-tools: bash)), nothing it rates as a warning. It is not a guarantee. The check reads SKILL.md only: the scripts in the folder are not scanned, so read them before running anything.

What licence does Building Skills use?

No licence was found for Building Skills or its repository. Without one, default copyright applies: ask the author before reusing or redistributing it.

How many tokens does Building Skills use?

About 4k tokens (SKILL.md is roughly 16k characters). Agents keep only the skill's name and description in context until a task matches; then they load SKILL.md in full. Its references folder adds about 1.6k tokens, read only when the agent opens those files.

What are the alternatives to Building Skills?

Skills that share tags, products or a category with Building Skills: Gameobject Modify (IvanMurzak/Unity-MCP, 4.4k stars), Object Modify (IvanMurzak/Unity-MCP, 4.4k stars), Assets Modify (IvanMurzak/Unity-MCP, 4.4k stars) and Modifying Taxonomic Filter (PostHog/posthog, 40k stars). The comparison table on this page puts their stars, adoption, token cost, safety result and licence side by side.

Who maintains Building Skills?

aiskillstore (a GitHub organization) maintains it in aiskillstore/marketplace, which has 433 GitHub stars. The repository holds 1,044 skills in this directory. The repository was last updated on October 10, 2026.

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