Getting it into your agent
This one installs as part of its plugin. Adding the marketplace and installing the plugin brings it with everything else the plugin ships.
/plugin marketplace add V-Songbird/slag/plugin install assayWrote 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/v-songbird/slag/craft-skill)<a href="https://agentmods.dev/skills/v-songbird/slag/craft-skill"><img src="https://agentmods.dev/badge/skills/v-songbird/slag/craft-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/v-songbird/slag/craft-skill"><img src="https://agentmods.dev/badge/skills/v-songbird/slag/craft-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 | $0.00142 | $0.02749 |
| Opus 5 | $0.00071 | $0.01375 |
| Sonnet 5 | $0.00028 | $0.00550 |
| Haiku 4.5 | $0.00014 | $0.00275 |
Grade A, and why
craft-skill 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 9d 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.
How it starts
The opening of the file, as written. The whole thing — 227 lines — stays where its author put it; the contents beside it link to each section on GitHub.
assay:craft-skill
You build one skill per run — new, or a refit of an existing one. $ARGUMENTS,
if present, names the skill or describes what it should do.
You never write a skill file yourself. Every artifact — the SKILL.md, any
metadata sidecar, a companion rule, a hook — goes through the engine's change
transaction in step 5, so each one is previewed before it lands and reversible
after.
1. Read the project
Before anything else, from the project root:
node "${CLAUDE_PLUGIN_ROOT}/scripts/assay.js" scan
If node is not on PATH (fnm/nvm setups), register it the way the project's
CLAUDE.md says to, then rerun.
Then read .assay-tmp/scan.json. Every fact below comes from it; never assume a
directory or a required field:
profile.targets.skill—dirandfile(where skills live),requires[](the frontmatter documented as required),metadata[](any invocation/UI sidecar), anddocs(the page to fetch in step 2).skills[]— every project skill already discovered, with itsname,path, andchecks. This is where a refit target comes from, and where a name collision shows up.coverage.skillBudget— the collective listing budget, where one is published. Every skill's name and description spend from it before any skill is selected, so a long description costs the whole list.profile.targets.hook.docs— the hooks page, for step 4's ladder.
2. Scope, and ground the format
Decide new-vs-refit: it is a refit when the user pointed at a skill in
skills[], or one there matches their words. Otherwise it is new.
Collect, from the conversation or one AskUserQuestion round at most. Don't
ask for what the user already said; only fill real gaps.
- What the skill does — enough to write a concrete base sentence naming real artifacts.
- Three or four ways the user would actually phrase the ask, in their words.
- The nearest adjacent ask the skill should NOT fire on.
- Whether the skill is bound to a file type or path (a candidate for a scoped companion rule).
- Which tools or commands the skill depends on.
- How critical firing is: nice-to-have, should-always-run, or must-never-be-skipped.
What ships with it
1 file 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.
- 9d ago First seen · 227 lines · 142 tokens per session scan A 7069078d42db
craft-skill is a skill published in the GitHub repository V-Songbird/slag (1 stars, last pushed 4d ago), licensed MIT. It adds 142 tokens to every session and 2,749 once invoked, about $0.0007 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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