skill_builder

skill_builder is a skill for Claude Code, Codex from jxoesneon/Ciel. It costs 21 tokens per session (303 once invoked), scanned A, original, Apache-2.0.

A tool for creating and packaging .skill files, which are ZIP bundles containing instructions and supporting metadata for an agent skill.

In plain words
What is it for?
Use it to scaffold a skill directory, create its instruction file and metadata, validate the contents, and build a distributable .skill ZIP.
Why use it?
It avoids assembling skill bundles by hand and provides checks for their structure and integrity.

Skill for Claude CodeCodex

Written for no agent in particular: nothing here depends on one.

Install

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.

agentmods
npx agentmods add skills/jxoesneon/ciel/skill_builder
Any agent
npx skills add jxoesneon/Ciel --skill skill_builder
Clone the repo
git clone --depth 1 https://github.com/jxoesneon/Ciel

Made for: Claude Code, Codex.

Wrote 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.

agentmods badge for skill_builder

README.md
[![agentmods](https://agentmods.dev/badge/skills/jxoesneon/ciel/skill_builder.svg)](https://agentmods.dev/skills/jxoesneon/ciel/skill_builder)
Your own site
<a href="https://agentmods.dev/skills/jxoesneon/ciel/skill_builder"><img src="https://agentmods.dev/badge/skills/jxoesneon/ciel/skill_builder.svg" alt="Measured on agentmods" height="20"></a>
Per session 21 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 303 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
Origin original No closer match found in the catalogue.
Token cost

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.

ModelPer sessionOnce invoked
Fable 5.1 $0.00021 $0.00303
Opus 5 $0.00010 $0.00151
Sonnet 5 $0.00004 $0.00061
Haiku 4.5 $0.00002 $0.00030

Measured 5d ago against content hash 8a1c77ec948c, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-06, from the pricing page.

Security

Grade A, and why

skill_builder 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 5d 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.

ciel.skill/seed_skills/skill_builder/SKILL.md · 37 lines

What it actually says

skill_builder

Create a new .skill bundle from structured input.

Operations

  • skill.new(spec) — scaffold directory from templates/skill.template.md.
  • skill.assemble(dir) — build ZIP (.skill) with checksum manifest.
  • skill.validate(dir) — schema + integrity check.
  • skill.frontmatter(parts) -> yaml — build frontmatter.

I/O Contract

io_contract:
  input: { op, "spec?", "dir?" }
  output: { path_or_bytes, report }
  idempotent: depends
  side_effects: [fs]

Integration

Used by acquisition/TIER_3_WEB.md for synthesis outputs, and by self_improvement/ for composing new registered skills from accumulated patterns.

Changes

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.

  1. 5d ago First seen · 37 lines · 21 tokens per session scan A 8a1c77ec948c

Subscribe to this mod's changes

skill_builder is a skill published in the GitHub repository jxoesneon/Ciel (1 stars, last pushed 5d ago), licensed Apache-2.0. It adds 21 tokens to every session and 303 once invoked, about $0.0001 per session on Opus 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 2026-08-31.

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