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-principlesgit 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-principles)<a href="https://agentmods.dev/skills/hoangnguyen0403/agent-skills-standard/system-design-principles"><img src="https://agentmods.dev/badge/skills/hoangnguyen0403/agent-skills-standard/system-design-principles/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-principles"><img src="https://agentmods.dev/badge/skills/hoangnguyen0403/agent-skills-standard/system-design-principles.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 | $0.00051 | $0.00726 |
| Opus 5 | $0.00026 | $0.00363 |
| Sonnet 5 | $0.00010 | $0.00145 |
| Haiku 4.5 | $0.00005 | $0.00073 |
Grade A, and why
system-design-principles 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 13d 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 — 80 lines — stays where its author put it; the contents beside it link to each section on GitHub.
System Design Principles
Priority: P0 (CRITICAL)
Workflow: Evaluate Architecture for New Feature
- Identify bounded contexts and module boundaries
- Name the data owner and define dependency direction (outer layers depend on inner)
- Select communication pattern (sync REST, async event, or hybrid) and failure behavior
- Validate CAP trade-offs only for distributed components
- Record boundary, trade-off, and rollback in an ADR
For a failing synchronous dependency, keep the critical path explicit: timeout and circuit-break the dependency, return a defined degraded/fallback result where safe, and move non-critical notifications to an asynchronous event.
Architectural Principles
- SoC: Divide into distinct sections per concern.
- SSOT: One source, reference elsewhere.
- Fail Fast: Fail visibly when errors occur.
- Graceful Degradation: Core functional even if secondary fails.
Modularity & Coupling
- High Cohesion: Related functionality in one module.
- Loose Coupling: Use interfaces for communication.
- DI: Inject dependencies, don't hardcode.
See implementation examples for dependency flow diagrams.
Common Patterns
- Layered: Presentation -> Logic -> Data.
- Event-Driven: Async communication between decoupled components.
- Clean/Hexagonal: Core logic independent of frameworks.
- Statelessness: Favor stateless for scaling/testing.
- Monolith first: Start modular-monolith; split a service out only when a module needs independent scaling, release cadence, or ownership.
Distributed Systems
- CAP: Trade-off Consistency/Availability/Partition tolerance. See CAP & Consistency Patterns.
- Idempotency: Operations repeatable without side effects. See Idempotency Patterns.
- Circuit Breaker: Fail fast on failing services. See Resilience Patterns.
- Eventual Consistency: Design for async data sync. See CAP & Consistency Patterns.
What ships with it
3 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.
- 13d ago First seen · 80 lines · 51 tokens per session scan A f5b25c01c147
system-design-principles is a skill published in the GitHub repository HoangNguyen0403/agent-skills-standard (565 stars, last pushed 3d ago), licensed MIT. It adds 51 tokens to every session and 726 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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server-setup
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