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 Light0305/Light-skills --skill light-system-designgit clone --depth 1 https://github.com/Light0305/Light-skillsWrote 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/light0305/light-skills/light-system-design)<a href="https://agentmods.dev/skills/light0305/light-skills/light-system-design"><img src="https://agentmods.dev/badge/skills/light0305/light-skills/light-system-design/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/light0305/light-skills/light-system-design"><img src="https://agentmods.dev/badge/skills/light0305/light-skills/light-system-design.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 | $0.00134 | $0.02968 |
| Opus 5 | $0.00067 | $0.01484 |
| Sonnet 5 | $0.00027 | $0.00594 |
| Haiku 4.5 | $0.00013 | $0.00297 |
Grade A, and why
light-system-design 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 9d 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 — 311 lines — stays where its author put it; the contents beside it link to each section on GitHub.
System design lifecycle
Own system boundaries, runtime interfaces, operational data stores, system migrations, and architecture decisions. Do not equate a diagram, SQL file, or OpenAPI document with a working, safe, or scalable system.
Read
references/system-design-resource-map.md
before any existing-system task. It defines the lifecycle, artifact contract,
decision stop, evidence states, access tiers, and cross-skill ownership. Read
references.md only for the database/API/reliability branch
that applies to the selected system.
Non-negotiable boundary
- Treat repository, configuration, schema, API, dependency, and deployment intake as read-only access. It is not authorization to rewrite them.
- Preserve absent facts as
UNKNOWN. Do not infer traffic, SLOs, consistency, budget, compliance, migration windows, or team capability from the phrase “system design.” - Present at least a recommendation, a viable alternative, and explicit rejection/exit conditions. Stop before choosing the database, topology, compatibility policy, or migration strategy for the user.
- Bind any later mutation to a user-selected option and exact authorized action IDs. Keep before/after locators, SHA-256, verification, and rollback.
- Never mutate a production database or configuration. Apply only to a disposable environment explicitly placed in scope; otherwise deliver a reviewed plan and scripts.
- Describe
schema_lint.pyas a lexical heuristic. It is not a SQL parser, query planner, lock simulator, schema diff engine, or zero-downtime proof. - Keep
VERIFIEDfor checks that actually ran and retain their command, return code, locator, and hash. UsePLANNED,UNKNOWN, orUNAVAILABLEotherwise. - Keep this skill off the research DAG. Emit no
light.findings.v1; add noSTAGE_GATES,ROUTES, stage number, or back-edge; do not attach_shared.
Choose the mode
| Situation | Mode |
|---|---|
| New system with no implementation | greenfield requirements and option design |
| Existing repository/system | read-only intake, then current-state inventory |
| Existing monolith or services changing gradually | modernization with compatibility and rollback |
| API-only change | contract and consumer compatibility branch |
| Schema-only change | dialect/version/context-specific migration branch |
| User supplied a completed package | review and evidence verification |
What ships with it
15 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.
- references.md 3.8 KB
- references/system-design-resource-map.md 8.9 KB
- scripts/architecture_lifecycle.py 30 KB runs code
- scripts/contract_validate.py 12 KB runs code
- scripts/design_readiness.py 34 KB runs code
- scripts/er_diagram.py 14 KB runs code
- scripts/schema_lint.py 35 KB runs code
- templates/architecture-package.template.md 1.8 KB
- templates/decision-authorization.template.json 424 B
- templates/design-readiness.example.json 3.2 KB
- templates/migration_expand_contract.sql 1.3 KB
- templates/openapi.yaml 4.2 KB
- templates/rls_policy.sql 981 B
- templates/schema.sql 1.1 KB
- templates/system-intake.template.json 931 B
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.
- 9d ago First seen · 311 lines · 134 tokens per session scan A 0bc3fff35e9a
light-system-design is a skill published in the GitHub repository Light0305/Light-skills (610 stars, last pushed 2mo ago), licensed MIT. It adds 134 tokens to every session and 2,968 once invoked, about $0.0007 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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