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/monkilabs/opencastle/sentrynpx skills add monkilabs/opencastle --skill sentrygit clone --depth 1 https://github.com/monkilabs/opencastleWhat 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 | $0.00054 | $0.00506 |
| Opus 5 | $0.00027 | $0.00253 |
| Sonnet 5 | $0.00011 | $0.00101 |
| Haiku 4.5 | $0.00005 | $0.00051 |
Grade A, and why
sentry-monitoring 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 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.
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.
What it actually says
Sentry Monitoring
Next.js
- Three separate init files, and the browser one is
instrumentation-client.ts— notsentry.client.config.ts— alongsidesentry.server.config.tsandsentry.edge.config.ts.npx @sentry/wizard@latest -i nextjscreates all three and patchesnext.config.ts. - Source maps upload only when
next.config.tsis wrapped inwithSentryConfig()andSENTRY_AUTH_TOKEN(plusSENTRY_ORG/SENTRY_PROJECT) is present at build time, CI included. tunnelRoute: '/monitoring'proxies events through your own origin so ad-blockers stop dropping them.app/global-error.tsxreports nothing by itself — callSentry.captureException(error)inside it. Wrap server actions inSentry.withServerActionInstrumentation('name', fn).
Node / Express
import './instrument' must come before every other import in the process. app.use(Sentry.expressErrorHandler()) must be the last error-handling middleware.
Sampling and context
tracesSampleRate: 1.0 dev, 0.2–0.5 low-traffic production, 0.05–0.1 high-traffic. UsetracesSamplerreturning 0 for/healthand polling routes, ~0.5 for checkout/auth.Sentry.setUser/setTag/setContextpersist for the rest of the session;Sentry.withScopeis one-off. Re-throw aftercaptureExceptionwhen the caller still needs the error.- Override issue grouping with
event.fingerprint = [...]inbeforeSend. - Core Web Vitals are captured with no config. Alert thresholds: LCP > 2.5s, CLS > 0.1, INP > 200ms.
- The DSN is safe to expose client-side.
sendDefaultPii: truecaptures IP, user agent, and authenticated user.
Docs: https://docs.sentry.io/
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.
- 2d ago First seen · 28 lines · 54 tokens per session scan A f33b55cde47e
sentry-monitoring is a skill published in the GitHub repository monkilabs/opencastle (61 stars, last pushed 4d ago), licensed MIT. It adds 54 tokens to every session and 506 once invoked, about $0.0003 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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