x9-skill-creator

x9-skill-creator is a skill for Claude Code from xonika9/agent-skills. It costs 89 tokens per session (1,431 once invoked), scanned A, original, MIT.

A skill for creating, checking, repairing, or improving agent skills for Claude Code or Codex. It evaluates triggers, instructions, resources, safety, and validation.

In plain words
What is it for?
Use it when authoring or auditing a SKILL.md and its related files, including checking how instructions are organized and how the skill is activated.
Why use it?
It helps ensure a skill is discoverable, appropriately scoped, safe to run, and clear enough for an agent to follow consistently.

Skill for Claude Code

Written for Claude Code: shipped in a Claude Code plugin. Also seen: mentions Claude Code; mentions Codex.

Part of the x9-agent-skills plugin — 18 skills shipped together

Good fit Use it when authoring or auditing a SKILL.md and its related files, including checking how instructions are organized and how the skill is activated.

Compare 6 skills from other repositories ↓
Install with agentmods
npx agentmods add skills/xonika9/agent-skills/x9-skill-creator
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.

Any agent
npx skills add xonika9/agent-skills --skill x9-skill-creator
Clone the repo
git clone --depth 1 https://github.com/xonika9/agent-skills

Made for: Claude Code.

Or install x9-agent-skills, the plugin that ships this one along with the rest of its 18 skills.

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 x9-skill-creator

README.md
[![agentmods](https://agentmods.dev/badge/skills/xonika9/agent-skills/x9-skill-creator/github.svg)](https://agentmods.dev/skills/xonika9/agent-skills/x9-skill-creator)
Your own site
<a href="https://agentmods.dev/skills/xonika9/agent-skills/x9-skill-creator"><img src="https://agentmods.dev/badge/skills/xonika9/agent-skills/x9-skill-creator/github.svg" alt="Measured on agentmods" height="20"></a>

Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.

agentmods 80×15 button for x9-skill-creator

Your own site · 80×15
<a href="https://agentmods.dev/skills/xonika9/agent-skills/x9-skill-creator"><img src="https://agentmods.dev/badge/skills/xonika9/agent-skills/x9-skill-creator.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 89 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 1,431 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. A grade says what 26 rules found in the file — not that it is safe.
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 $0.00089 $0.01431
Opus 5 $0.00044 $0.00715
Sonnet 5 $0.00018 $0.00286
Haiku 4.5 $0.00009 $0.00143

Measured 10d ago against content hash 9135f2bc7dae, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-09, from the pricing page.

Security

Grade A, and why

x9-skill-creator 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 10d ago.

The scan reads SKILL.md. This mod also ships 2 executable files (scripts/test_validate.py, scripts/validate.py), listed below but not scanned — reading those needs a real analyzer, not pattern matching.

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.

skills/x9-skill-creator/SKILL.md · 82 lines

How it starts

The opening of the file, as written. The whole thing — 82 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Skill creator

Create and audit skills through one cross-runtime quality contract: precise triggering, appropriate freedom, safe authority, progressive disclosure, and evidence proportional to maturity and risk.

The machine-readable onboarding contract lists external prerequisites.

The body of a skill and some reachable resources are agent instructions. For every Create, Audit, or Fix, load and apply x9-agent-instructions before writing or judging any agent-facing instructional prose in SKILL.md or reachable resources. It is a subordinate rubric, not the primary skill-authoring workflow, and it owns language, prescription, duplication, and what earns a line. This skill owns what makes the instruction a skill: triggering metadata, placement and runtime adapters, resource layout and progressive disclosure, evidence tier, structural validation, and the audit handoff.

If x9-agent-instructions is unavailable, continue only the remaining skill checks, record the instruction rubric as degraded, and do not claim that instruction quality was reviewed. A full skill audit cannot be clean in that state. Work whose explicit scope contains no agent-facing prose may record the rubric as not applicable.

Select action and evidence

Choose the action first:

  • Create: the target skill does not exist or the user requests a new one.
  • Audit: inspect an existing skill, read the complete skill and reachable resources, validate structure, and report findings without changing files.
  • Fix: apply explicitly authorized improvements to an existing skill, then recheck the changed contract.

Choose the evidence tier separately:

  • Static (default): inspect files, run structural validation, and judge contracts and dependencies without live model invocations.
  • Behavioral (optional): run clean-context scenarios from references/evals.md when the user requests live evaluation or a stable/shared/high-risk skill needs behavioral proof for a load-bearing claim.

Read the full file on GitHub · 82 lines

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. 10d ago First seen · 82 lines · 89 tokens per session scan A 9135f2bc7dae

Subscribe to this mod's changes

x9-skill-creator is a skill published in the GitHub repository xonika9/agent-skills (4 stars, last pushed 4d ago), licensed MIT. It adds 89 tokens to every session and 1,431 once invoked, about $0.0004 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.