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 volodchenkov/claude-sdlc-agents --skill system-design-techniquesgit clone --depth 1 https://github.com/volodchenkov/claude-sdlc-agentsWrote 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/volodchenkov/claude-sdlc-agents/system-design-techniques)<a href="https://agentmods.dev/skills/volodchenkov/claude-sdlc-agents/system-design-techniques"><img src="https://agentmods.dev/badge/skills/volodchenkov/claude-sdlc-agents/system-design-techniques/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/volodchenkov/claude-sdlc-agents/system-design-techniques"><img src="https://agentmods.dev/badge/skills/volodchenkov/claude-sdlc-agents/system-design-techniques.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 | $0.00071 | $0.02725 |
| Opus 5 | $0.00036 | $0.01362 |
| Sonnet 5 | $0.00014 | $0.00545 |
| Haiku 4.5 | $0.00007 | $0.00272 |
Grade A, and why
system-design-techniques 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 8d 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 — 244 lines — stays where its author put it; the contents beside it link to each section on GitHub.
System Design Techniques — SA reference
This skill encodes industry-standard system analysis techniques used by the system-analyst. Inspired by:
- C4 Model (Simon Brown) — architecture diagrams at multiple zoom levels
- DDD (Eric Evans, Vaughn Vernon) — bounded contexts, ubiquitous language
- REST design (Roy Fielding, Mark Massé "REST API Design Rulebook")
- IEEE 29148:2018 — Systems and software engineering — Requirements engineering
- ADR (Michael Nygard) — Architecture Decision Records
We use a focused subset — enough discipline to make SPEC professional and traceable, without ceremony overhead.
C4 Model — for the "Affected services" / "Architecture" sections
C4 has four zoom levels. The system-analyst uses two:
Level 1: System Context
Who interacts with the system from outside? Single box for our system, surrounded by external actors and external systems.
The project's $KB_DIR/kb/architecture.md lists the external actors and integrations — use it as the source.
Use Mermaid to draw it (Plane renders Mermaid in markdown):
flowchart LR
Customer((Customer)) --> Storefront[<frontend-app>]
Operator((Internal user)) --> Console[<admin-app>]
Storefront & Console --> API[<backend-app>]
API --> ExternalA[<external integration>]
API --> ExternalB[<payment / delivery / object storage / …>]
In SPEC: include this only when the change affects the system boundary (new external integration, new actor type). Otherwise skip.
Level 2: Container view
Inside the system — what runs separately. Backend services + workers + cache + database + frontends.
Use only when change spans multiple containers (e.g. new background task that interacts with API + cache).
Levels 3 (Component) and 4 (Code)
Skip in SPEC. Component-level structure is for code review (architect's ARCH_REVIEW or coder's PLAN). Don't pre-implement in SPEC.
DDD — Bounded Contexts mapped to project services
Domain-Driven Design's most useful concept is bounded context: a logical boundary inside which a domain model is consistent. Each project service / app is a bounded context.
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.
- 8d ago First seen · 244 lines · 71 tokens per session scan A 9e57012624e5
system-design-techniques is a skill published in the GitHub repository volodchenkov/claude-sdlc-agents (2 stars, last pushed 1mo ago), licensed MIT. It adds 71 tokens to every session and 2,725 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 2026-08-31.
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