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 mblode/agent-skills --skill app-verificationgit clone --depth 1 https://github.com/mblode/agent-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/mblode/agent-skills/app-verification)<a href="https://agentmods.dev/skills/mblode/agent-skills/app-verification"><img src="https://agentmods.dev/badge/skills/mblode/agent-skills/app-verification/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/mblode/agent-skills/app-verification"><img src="https://agentmods.dev/badge/skills/mblode/agent-skills/app-verification.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 | $0.00069 | $0.02102 |
| Opus 5.5 | $0.00028 | $0.00841 |
| Sonnet 5.5 | $0.00014 | $0.00420 |
| Haiku 4.5 | $0.00007 | $0.00210 |
Grade A, and why
app-verification 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 5d 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 — 103 lines — stays where its author put it; the contents beside it link to each section on GitHub.
App Verification
Builds, inside a product's own repository, the harness every agent uses to run that product and prove a claim about it: a verify CLI, a doctor command, an isolated instance per worktree, a feature map written from the user's point of view, seed data and test accounts, and a reproduce-first bug handoff. The harness lives in the target repo, not in this skill; this skill scaffolds and then maintains it, so every agent that opens that repo runs the app the same way instead of writing a throwaway script each session.
- IS: scaffolding a project-local verification harness (Create mode) and running or extending one that already exists (Maintain mode): the verify CLI's contract, the feature-map format, the proof record, per-worktree isolation and seed data, the cheapest-method ladder up to computer use, and the bug-handoff format.
- IS NOT: ad hoc browser probes against a fixed catalogue of UI rules (
ui-verification; this skill'sverifycan call those probes as one check among several), repo-wide module boundaries and enforcement tooling (codebase-architecture; this skill's CI wiring follows its enforcement order), pruning an existing test suite (test-audit), or a plan for one feature (planning).
Invocation
Create mode edits the target repo and Maintain mode drives a real running instance of it; both run only when named, not from a loose "check the app" prompt a lighter skill might serve better. On a host that supports it, add disable-model-invocation: true to the installed copy's frontmatter. It is a host extension, not a portable field, so it is not shipped in this source (agent-skills-creator's references/format-specification.md explains why). Hosts with an equivalent explicit-invocation setting should apply it the same way.
Contents
What ships with it
7 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.
- 5d ago Changed · -3 lines · -56 tokens per session 02bc8734daa8
- 12d ago First seen · 106 lines · 125 tokens per session scan A 4ad12982ec68
app-verification is a skill published in the GitHub repository mblode/agent-skills (144 stars, last pushed yesterday), licensed MIT. It adds 69 tokens to every session and 2,102 once invoked, about $0.0003 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 2026-09-28.
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Use when the user says 'write browser tests', 'test this page', 'playwright test', 'e2e test', 'end to end test', 'browser test', 'test the UI', or needs Playwright-based browser testing for a web application. Do NOT use for unit tests, API tests, or non-browser testing.
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