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.
npx skills add davekilleen/Dex --skill create-skillgit clone --depth 1 https://github.com/davekilleen/DexWrote 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.
[](https://agentmods.dev/skills/davekilleen/dex/create-skill)<a href="https://agentmods.dev/skills/davekilleen/dex/create-skill"><img src="https://agentmods.dev/badge/skills/davekilleen/dex/create-skill/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.
<a href="https://agentmods.dev/skills/davekilleen/dex/create-skill"><img src="https://agentmods.dev/badge/skills/davekilleen/dex/create-skill.svg" alt="Reviewed on agentmods" width="80" height="20"></a>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.
| Model | Per session | Once invoked |
|---|---|---|
| Fable 5.1 | $0.00189 | $0.02883 |
| Opus 5.5 | $0.00076 | $0.01153 |
| Sonnet 5.5 | $0.00038 | $0.00577 |
| Haiku 4.5 | $0.00019 | $0.00288 |
Grade B, and why
create-skill scanned grade B with 1 finding 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 25d 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.
Subtle steeringmediumPrompt injection
Instructions that bias recommendations or shape behaviour without the user noticing.
**Slash-path honesty:** Claude Code only dispatches `/name` for skills it loaded from `.claude/skills/`, `~/.claude/skills/`, `.claude/commands/`, or a plugin (`/plugin-name:skill-name`). A user skill under `.claude/skil How it starts
The opening of the file, as written. The whole thing — 143 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Create a Skill
Author a skill the way the router and a real user will experience it: it must fire when it should (the description is the router) and do the job safely and well when it fires (the body is a contract, not a how-to essay). This skill runs a real authoring sequence — collision → classify → contract → generate → validate → score — and does not declare done until skill-score has graded the package.
Slash-path honesty: Claude Code only dispatches /name for skills it loaded from .claude/skills/, ~/.claude/skills/, .claude/commands/, or a plugin (/plugin-name:skill-name). A user skill under .claude/skills-custom/ is not on that list. Never tell the user to type /{name} or /{name}-custom for a skills-custom folder. Ask them to use the trigger phrases instead.
Governing principle: hard on Core, gentle on the user's own creations. A first-party (Core) skill must pass skill-score ≥ 85 to ship — a hard gate we hold ourselves to. A skill the user writes for themselves is coached, never blocked: show the score, name the one change that would make it fire, offer to make it — but always create/keep their skill if they want it.
Compose, don't fork: anthropic-skill-creator (vendored) is the general skill-authoring guide; the Dex-specific delta lives in references/dex-skill-standard.md. Read that reference before generating the package.
Step 1 — Get intent
Ask the user for:
1. A short name (e.g. "meeting-notes", "board-update") — hyphens, no spaces
2. What it should do for you, in 1–2 sentences
3. When you'd want it to fire — the phrases you'd actually say
Point 3 is not optional — it is the raw material for the WHEN trigger. If the user only gives 1–2, ask for the trigger phrases before continuing.
Step 2 — Determine origin
- User skill (the default in an end-user vault): the user is building this for themselves. Write it at
.claude/skills-custom/{name}/. That directory is vault-owned, so updates never overwrite it. The skill is coached, never blocked. Do not put it under.claude/skills/, and do not add-customto the folder name unless{name}already belongs to a shipped skill. - First-party / Core skill (authoring inside the Dex repo, to ship to everyone): authored under
.claude/skills/{name}/and held to the hard gate (skill-score ≥ 85).
What ships with it
2 files beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.
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.
- 25d ago Changed · +7 lines · +30 tokens per session scan A → B d26589ae01cf
- 1mo ago Changed 4a6092982deb
- 1mo ago Changed · +2 lines · +4 tokens per session d0157df8f8b0
- 1mo ago First seen · 134 lines · 155 tokens per session scan A 0a5a30e105ab
create-skill is a skill published in the GitHub repository davekilleen/Dex (507 stars, last pushed today), licensed MIT. It adds 189 tokens to every session and 2,883 once invoked, about $0.0008 per session on Opus 5.5. A static security scan graded it B with 1 finding (subtle steering). No closer match exists in the catalogue, so it is treated as the original; first seen 2026-09-03.
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