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 HoangNguyen0403/agent-skills-standard --skill system-design-mobile-clientgit clone --depth 1 https://github.com/HoangNguyen0403/agent-skills-standardWrote 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/hoangnguyen0403/agent-skills-standard/system-design-mobile-client)<a href="https://agentmods.dev/skills/hoangnguyen0403/agent-skills-standard/system-design-mobile-client"><img src="https://agentmods.dev/badge/skills/hoangnguyen0403/agent-skills-standard/system-design-mobile-client/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/hoangnguyen0403/agent-skills-standard/system-design-mobile-client"><img src="https://agentmods.dev/badge/skills/hoangnguyen0403/agent-skills-standard/system-design-mobile-client.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 | $0.00060 | $0.00600 |
| Opus 5.5 | $0.00024 | $0.00240 |
| Sonnet 5.5 | $0.00012 | $0.00120 |
| Haiku 4.5 | $0.00006 | $0.00060 |
Grade A, and why
system-design-mobile-client 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.
How it starts
The opening of the file, as written. The whole thing — 37 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Mobile and Client System Design
Priority: P1 (HIGH)
Classify the work mode independently from its surface: new design, review existing, or interview practice can each target mobile/client, SDK/library, backend, or full stack. Focus on user-visible authority, lifecycle, synchronization, platform constraints, and host compatibility—not UI/framework implementation.
Design decisions
- Name the server-authoritative state and any local display, pending, cached, or derived state. Never present optimistic/pending state as durable server success.
- For each critical client flow, link the canonical critical-flow contract; do not duplicate its field checklist. Add only material client-specific lifecycle, auth, freshness, retry, conflict, and deletion decisions.
- Decide explicitly whether offline use is required. If correctness depends on a live authorization or current server state, choose online-only behavior and define unavailable/error UX; do not add a local database by default.
- If offline writes are allowed, define pending/confirmed/failed outcomes, stable operation identity, retry and deduplication, conflict resolution, freshness, account-switch/logout handling, and deletion of local and server copies.
- Bound device work: memory, disk, network, battery-sensitive work, queue growth, payload size, and resource release. Estimate only quantities relevant to the stated workload.
- Treat secure storage and authentication as trust-boundary choices: limit token and sensitive-data persistence, bind queued work to its account, and prevent replay after logout or account change.
- Select a dataflow, sequence, state, or deployment view only when it answers a named decision; prose or a table is sufficient otherwise.
For client authority, sync, authentication changes, or deletion decisions, load the client authority and lifecycle contract. For a reusable client library, cover its public contract, compatibility, cancellation, concurrency ownership, bounded resource use, host integration, lifecycle, and failure results; see SDK contract. For OS scheduling and persistence constraints, consult platform constraints. Framework-specific coding recipes are out of scope.
What ships with it
5 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.
- 2d ago First seen · 37 lines · 60 tokens per session scan A 619d75766957
system-design-mobile-client is a skill published in the GitHub repository HoangNguyen0403/agent-skills-standard (581 stars, last pushed today), licensed MIT. It adds 60 tokens to every session and 600 once invoked, about $0.0002 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 2026-10-22.
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