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 agentmods add skills/understudylabs/understudy-agent-tools/install-codex-pluginnpx skills add understudylabs/understudy-agent-tools --skill install-codex-plugingit clone --depth 1 https://github.com/understudylabs/understudy-agent-toolsWhat 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 | $0.00072 | $0.00431 |
| Opus 5 | $0.00036 | $0.00216 |
| Sonnet 5 | $0.00014 | $0.00086 |
| Haiku 4.5 | $0.00007 | $0.00043 |
Grade B, and why
install-codex-plugin scanned grade B with 1 finding against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 2d ago.
A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.
Reads agent configuration directoriesmediumAgent snooping
.claude/, .codex/, .gemini/ hold keys, settings and other credentials a mod has no legitimate need for.
- Do not edit `~/.codex/config.toml` by hand unless the user explicitly asks. What it actually says
Install the Understudy Codex plugin
This skill is a compatibility shim. The consolidated setup surface is
install-agent-adapter.
Procedure
Load install-agent-adapter and run it with platform codex.
Use its reference.md for the
current marketplace registration:
codex plugin marketplace add "$REPO"
Activation is in Codex:
/plugins
Choose understudy-skills, install or enable understudy, then ask:
Use the Understudy onboarding skill for this project.
Safety Gates
Local-first and free: registering the Codex marketplace only makes local skills available. It must not authenticate, upload data, inspect secret values, download model weights, start hosted jobs, or make provider calls.
- Do not claim the plugin is installed when only the marketplace is registered.
- Do not edit
~/.codex/config.tomlby hand unless the user explicitly asks. - Do not copy or fork skill content for Codex.
Resolve CLI
No Understudy CLI command is required. Use codex plugin marketplace add when
available; otherwise show the manual /plugins activation path from
install-agent-adapter/reference.md.
Output Standard
End with: that this routed through install-agent-adapter; whether the Codex
marketplace was registered/refreshed/shown for manual run; the /plugins step;
the next onboarding prompt; and the marketplace removal command.
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.
- 2d ago First seen · 60 lines · 72 tokens per session scan B 1995c5cc13c5
install-codex-plugin is a skill published in the GitHub repository understudylabs/understudy-agent-tools (16 stars, last pushed 3d ago), licensed MIT. It adds 72 tokens to every session and 431 once invoked, about $0.0004 per session on Opus 5. A static security scan graded it B with 1 finding (reads agent configuration directories). No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.
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