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 richfrem/agent-plugins-skills --skill authoring-subagentsgit clone --depth 1 https://github.com/richfrem/agent-plugins-skillsWrote 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/richfrem/agent-plugins-skills/authoring-subagents)<a href="https://agentmods.dev/skills/richfrem/agent-plugins-skills/authoring-subagents"><img src="https://agentmods.dev/badge/skills/richfrem/agent-plugins-skills/authoring-subagents/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/richfrem/agent-plugins-skills/authoring-subagents"><img src="https://agentmods.dev/badge/skills/richfrem/agent-plugins-skills/authoring-subagents.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 | $0.00099 | $0.00912 |
| Opus 5.5 | $0.00040 | $0.00365 |
| Sonnet 5.5 | $0.00020 | $0.00182 |
| Haiku 4.5 | $0.00010 | $0.00091 |
Grade A, and why
authoring-subagents 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 today.
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 — 63 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Authoring Sub-Agents (authoring-subagents)
Scaffolds sub-agent files and audits them against the authoring contract. Sub-agents are the exception, not the default.
Contents
- Constraints • Modes • Quick start • Workflow • Verification • References
Constraints
- Only three reasons justify a sub-agent: an isolated execution context, a sandboxed tool set, or an adversarial persona. Anything interactive, multi-turn or procedural is a skill.
- No pointer wrappers: an agent that only delegates to a skill must not exist.
- Explicit tool bounds and denial rules; the definition is self-contained and never depends on a source checkout.
- Model choices are not made here: the
modelfield defaults toinherit; model names and tiers belong to thecli-agentskill. - Plugin agents are flat files at
plugins/<plugin>/agents/<name>.md; project agents live in.claude/agents/<name>.md. - Audits are read-only.
Modes
| Mode | Use when | Entry point | Reference |
|---|---|---|---|
create |
New sub-agent | scripts/scaffold_subagent.py, then scripts/validate_agent.py |
create-sub-agent.md |
audit |
Check one agent or a whole plugin | scripts/audit_sub_agent.py |
audit-sub-agent.md |
Quick start
python3 scripts/scaffold_subagent.py --name <agent-name> --path plugins/<plugin>/agents --desc "<use-case>"
python3 scripts/validate_agent.py plugins/<plugin>/agents/<agent-name>.md
python3 scripts/audit_sub_agent.py plugins/<plugin> --all --json
Workflow
- Run the pre-design gate: does one of the three reasons apply? If not, create a skill instead.
- Scaffold, then write the system prompt in second person using system-prompt-design.md; add 2-4
<example>trigger blocks. - Validate and audit until zero errors; test at least three positive and three negative trigger prompts.
- Publish per agent-discovery-and-publication.md. On failure follow fallback-tree.md.
What ships with it
15 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.
- assets/templates/agent.md.jinja 957 B
- evals/evals.json 1.8 KB
- references/acceptance-criteria.md 1.3 KB
- references/agent-creation-prompt.md 9.7 KB
- references/agent-discovery-and-publication.md 2.0 KB
- references/complete-agent-examples.md 14 KB
- references/fallback-tree.md 1.8 KB
- references/modes/audit-sub-agent.md 2.4 KB
- references/modes/create-sub-agent.md 3.4 KB
- references/sub-agents-spec.md 3.3 KB
- references/system-prompt-design.md 10 KB
- scripts/audit_sub_agent.py 13 KB runs code
- scripts/scaffold_subagent.py 2.1 KB runs code
- scripts/validate_agent.py 9.6 KB runs code
- tests/test_scaffold_subagent.py 2.3 KB runs code
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.
- today First seen · 63 lines · 99 tokens per session scan A 63402fa73e2e
authoring-subagents is a skill published in the GitHub repository richfrem/agent-plugins-skills (7 stars, last pushed yesterday), licensed MIT. It adds 99 tokens to every session and 912 once invoked, about $0.0004 per session on Opus 5.5. 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 2026-10-24.
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