Borrowing it
Nothing to install: this file belongs to jfarcand/mirroir-mcp. 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/jfarcand/mirroir-mcp/main/.claude/skills/mirroir-onboard/SKILL.mdgit clone --depth 1 https://github.com/jfarcand/mirroir-mcpWrote 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/jfarcand/mirroir-mcp/mirroir-onboard)<a href="https://agentmods.dev/skills/jfarcand/mirroir-mcp/mirroir-onboard"><img src="https://agentmods.dev/badge/skills/jfarcand/mirroir-mcp/mirroir-onboard/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/jfarcand/mirroir-mcp/mirroir-onboard"><img src="https://agentmods.dev/badge/skills/jfarcand/mirroir-mcp/mirroir-onboard.svg" alt="Reviewed on agentmods" width="80" height="20"></a>- NVIDIA SkillSpector pass
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 | $0.00085 | $0.03824 |
| Opus 5 | $0.00043 | $0.01912 |
| Sonnet 5 | $0.00017 | $0.00765 |
| Haiku 4.5 | $0.00009 | $0.00382 |
Grade A, and why
mirroir-onboard 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 — 306 lines — stays where its author put it; the contents beside it link to each section on GitHub.
mirroir-onboard
You are the web explorer. You drive a consumer's running web app the way
an agent drives an iPhone in generate_skill action=explore: navigate, read
the live accessibility tree, find each surface's primary action, derive the
exact selector that resolves it, execute it, capture the resulting state change,
and emit a replayable .mirroir/ suite. Then you prove it by live replay
and self-heal any selector that doesn't resolve.
The output is a .mirroir/ tree at the consumer root that goes green under
mirroir-run (a real boot + real Playwright replay against the real backend),
not merely one that compiles. Compile-clean is necessary but not sufficient —
selectors that pass --emit playwright still fail at replay (wrong element,
strict-mode, or never resolves). The replay is the gate.
You do not hand-author from spec files. Every selector comes from a DOM you
observed via mcp__chrome-devtools__take_snapshot. You are mechanizing the
human loop, not transcribing a test plan.
What makes this worth doing (read before you start)
A mocked Playwright/Cypress suite (page.route(...)) verifies the frontend in
isolation — it stays green even when the backend wiring, DB seed, auth gate,
dev proxy, or LLM path is broken. mirroir's only job is to catch exactly those:
"the real stack boots and the headline journeys actually work." If your
scenarios don't exercise real primary actions against the real backend, you've
rebuilt the mocked suite slower — delete them and stop.
So: complementary, never a replacement. Run
find <root> -name '*.spec.ts' -o -name '*.cy.ts' | grep -v node_modules | wc -l
first; if non-zero, the mirroir.yaml description must say "complementary" and
name that count. Assume an existing suite exists until proven otherwise.
Phase 0 — Get the app to a usable, logged-in-able state
This is the phase that silently eats hours. A web app being "up on :PORT" does not mean a real user can log in and reach an authenticated surface. Confirm each link of the chain before exploring, because every one of these has bitten real onboarding:
What ships with it
1 file 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.
- 12d ago First seen · 306 lines · 85 tokens per session scan A f2bd1f058bbd
mirroir-onboard is a skill published in the GitHub repository jfarcand/mirroir-mcp (214 stars, last pushed 2d ago), licensed Apache-2.0. It adds 85 tokens to every session and 3,824 once invoked, about $0.0004 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 2026-08-30.
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