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 randommonicle/claude-skills --skill verify-the-effectgit clone --depth 1 https://github.com/randommonicle/claude-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/randommonicle/claude-skills/verify-the-effect)<a href="https://agentmods.dev/skills/randommonicle/claude-skills/verify-the-effect"><img src="https://agentmods.dev/badge/skills/randommonicle/claude-skills/verify-the-effect/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/randommonicle/claude-skills/verify-the-effect"><img src="https://agentmods.dev/badge/skills/randommonicle/claude-skills/verify-the-effect.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 | $0.00113 | $0.00742 |
| Opus 5 | $0.00056 | $0.00371 |
| Sonnet 5 | $0.00023 | $0.00148 |
| Haiku 4.5 | $0.00011 | $0.00074 |
Grade A, and why
verify-the-effect 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 — 52 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Verify the effect
The most recurrent failure in the lessons corpus (~nine ASH incidents plus the ICC email family): a success indicator that was true while the effect was absent. A green CI signing step that signed nothing. A report that "generated and emailed" while silently missing five sections. An HTTP 200 password change that never changed the password. "Accepted by Resend" masking a bounce. A served Content-Type differing from the uploaded one. Layer: norm + playbook — the one-line norm in the global CLAUDE.md is the everyday trigger; this file is the depth behind it.
The rule
A success indicator that can be true while the effect is absent proves nothing. Identify the real intended effect of the operation — the file signed, the row written, the email delivered, the section rendered, the password actually changed — and assert that.
How to apply
- Side-effect steps assert the side effect. Any step whose entire job is a side effect (signing, uploading, sending, publishing) gets an explicit post-step assertion: list the signature, HEAD the URL, read the delivery status. "The step was green" is not evidence — a Codemagic signing step once succeeded having signed nothing.
- Verify the artifact the user receives, not the pipeline's account of it: count its sections, count its photos, open the download link, check the served header rather than the uploaded one. A report can generate, email, and be missing half its content.
- Sensitive mutations are verified by using the result — sign in with the new password, read back the changed row — never by the response code. A WebView once returned 200 for a password change that silently no-opped.
- Diagnose from ground truth before theorising: server and auth logs, breadcrumbs, CI step durations (a two-second step that must call a remote API didn't call it), the running database, live object definitions. A working login proves only that one backend is reachable.
- Acceptance is not delivery. A provider 2xx means queued. For transactional email, load email-delivery-verification — the provider-specific child of this rule.
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 · 52 lines · 113 tokens per session scan A 66e7481724c9
verify-the-effect is a skill published in the GitHub repository randommonicle/claude-skills (23 stars, last pushed 5d ago), licensed Apache-2.0. It adds 113 tokens to every session and 742 once invoked, about $0.0006 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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