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 product-on-purpose/agent-skills-toolkit --skill askit-build-subagentgit clone --depth 1 https://github.com/product-on-purpose/agent-skills-toolkitWrote 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/product-on-purpose/agent-skills-toolkit/askit-build-subagent)<a href="https://agentmods.dev/skills/product-on-purpose/agent-skills-toolkit/askit-build-subagent"><img src="https://agentmods.dev/badge/skills/product-on-purpose/agent-skills-toolkit/askit-build-subagent/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/product-on-purpose/agent-skills-toolkit/askit-build-subagent"><img src="https://agentmods.dev/badge/skills/product-on-purpose/agent-skills-toolkit/askit-build-subagent.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 | $0.00059 | $0.00930 |
| Opus 5 | $0.00030 | $0.00465 |
| Sonnet 5 | $0.00012 | $0.00186 |
| Haiku 4.5 | $0.00006 | $0.00093 |
Grade A, and why
askit-build-subagent 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 12d 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 — 34 lines — stays where its author put it; the contents beside it link to each section on GitHub.
askit-build-subagent
Purpose
Author conformant subagents. Two modes: create scaffolds a new agents/<name>.md (frontmatter + role body); improve raises an existing subagent toward the quality bar. Subagents are Claude-only for plugin distribution (Codex v0.135 plugins cannot ship [agents.*]; Standard sec 3.3), so this skill emits no Codex artifact. Authoring depth is in references/authoring-subagents.md.
When to use
When the user asks to create, scaffold, write, or improve a subagent (an agents/<name>.md delegate).
create mode
- Brief interview: ask for the subagent name (kebab-case), the bounded job it owns, the narrowest tools it needs, and which components (if any) it may invoke. Skip the interview if these inputs are already in context.
- Copy
templates/agent.mdintoagents/<name>.md. - Fill the frontmatter:
nameequal to the file basename; adescriptionthat states what AND when (Standard sec 8.1);toolsas the narrowest set (sec 9); optionalmodel;metadata.chainnaming the components it may invoke as a comma-separated string (the recommended shape - a YAML list is silently coerced to a string repr by the reference implementation, seeauthoring-chain-contracts.md; omitchainif there is none);metadata.version,metadata.tier,metadata.status, andmetadata.agent-targets: [claude](sec 3.3 - subagents are Claude-only for plugin distribution). - Do not write
hooks,mcpServers, orpermissionMode. Claude Code states plainly that "for security reasons,hooks,mcpServers, andpermissionModeare not supported for plugin-shipped agents" (plugins reference, read 2026-08-12). Writing one does not configure anything; the runtime refuses it, and the author is left believing otherwise. The supported set isname,description,model,effort,maxTurns,tools,disallowedTools,skills,memory,background, andisolation(whose only valid value isworktree). Marketplace scope reports this across every member of a catalogue. - Register the subagent in
library.jsoncomponents.subagentsas{ name, path, version, tier, status }. - If the subagent declares a
chain, add the entry toagents/_chain-permitted.yaml(<name>: [<invoked>, ...]) so S4 has no orphan. - Assess with
node scripts/evaluate.mjs . --jsonand iterate until 0 errors (S3 components index + S4 chain contract must be clean).
What ships with it
3 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.
- 12d ago First seen · 34 lines · 59 tokens per session scan A 22734d90267a
askit-build-subagent is a skill published in the GitHub repository product-on-purpose/agent-skills-toolkit (2 stars, last pushed yesterday), licensed Apache-2.0. It adds 59 tokens to every session and 930 once invoked, about $0.0003 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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