Borrowing it
Nothing to install: this file belongs to ritchiecarroll/go2cs. Take a copy, put it at the same path in your own repository, and replace the rules that are about this project with yours.
curl -O https://raw.githubusercontent.com/ritchiecarroll/go2cs/master/.claude/skills/mailbox/SKILL.mdgit clone --depth 1 https://github.com/ritchiecarroll/go2csWrote 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/ritchiecarroll/go2cs/mailbox)<a href="https://agentmods.dev/skills/ritchiecarroll/go2cs/mailbox"><img src="https://agentmods.dev/badge/skills/ritchiecarroll/go2cs/mailbox/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/ritchiecarroll/go2cs/mailbox"><img src="https://agentmods.dev/badge/skills/ritchiecarroll/go2cs/mailbox.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 | $0.00033 | $0.04333 |
| Opus 5 | $0.00016 | $0.02167 |
| Sonnet 5 | $0.00007 | $0.00867 |
| Haiku 4.5 | $0.00003 | $0.00433 |
Grade C, and why
mailbox scanned grade C 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 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.
Hidden instructionshighPrompt injection
Directives inside HTML comments, invisible characters or bidirectional overrides are read by the model and not by the person reviewing the file.
<!-- ⚠ 2026-09-04: a sibling's mailbox post swept a scrub lane's three uncommitted substitutions into its OWN commit, and a second sibling's tree operation then reverted the scrub lane's remaining files before they could The source is not reproduced here
A licence we could not identify
The repository carries a LICENSE file, but it is custom or dual enough that GitHub cannot name it and neither can this catalogue. Unknown terms are not permission, so the body is not copied here. Read the licence at the source and decide for yourself.
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 · 201 lines · 33 tokens per session scan C d8651f52af51
mailbox is a skill published in the GitHub repository ritchiecarroll/go2cs (399 stars, last pushed today), with no licence file. It adds 33 tokens to every session and 4,333 once invoked, about $0.0002 per session on Opus 5. A static security scan graded it C with 1 finding (hidden instructions). No closer match exists in the catalogue, so it is treated as the original; first seen 2026-09-13.
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