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 xonovex/platform --skill oop-guidegit clone --depth 1 https://github.com/xonovex/platformWrote 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/xonovex/platform/oop-guide)<a href="https://agentmods.dev/skills/xonovex/platform/oop-guide"><img src="https://agentmods.dev/badge/skills/xonovex/platform/oop-guide/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/xonovex/platform/oop-guide"><img src="https://agentmods.dev/badge/skills/xonovex/platform/oop-guide.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 | $0.00050 | $0.00450 |
| Opus 5.5 | $0.00020 | $0.00180 |
| Sonnet 5.5 | $0.00010 | $0.00090 |
| Haiku 4.5 | $0.00005 | $0.00045 |
Grade A, and why
oop-guide 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 7d 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 — 33 lines — stays where its author put it; the contents beside it link to each section on GitHub.
General Object-Oriented Programming Guidelines
Use composition, focused interfaces, and encapsulated state to keep object-oriented code easy to change.
Stances
- Prefer composition over inheritance; program to interfaces, reserving abstract classes for shared implementation.
- Keep state private; expose behavior through methods.
- SOLID: single responsibility, open/closed, Liskov substitution, interface segregation, dependency inversion.
- Apply patterns (Factory, Strategy, Observer) only when they simplify code, never speculatively.
Design smells
Recognizers for common OO-design problems and the principle each violates.
- God Object / Large Class: one class with many responsibilities and low cohesion; split by responsibility (single responsibility).
- Refused Bequest: a subclass that ignores or throws on inherited behavior breaks the base-class contract (Liskov substitution); prefer composition over that inheritance.
- Downcasting: a cast that asks "which subtype is this really?" breaks the abstraction and usually signals a Liskov violation; dispatch through the interface instead.
- Divergent Change: one class edited for many unrelated reasons; separate the reasons into focused classes (single responsibility).
- Parallel Inheritance Hierarchies: every new subclass in one tree forces a mirrored subclass in another; collapse or fold the hierarchies.
- Alternative Classes with Different Interfaces: two classes do the same job with unswappable signatures; unify the interface so callers don't choose sides.
- Temporary Field: a field populated only in some circumstances, empty otherwise; extract the conditional behavior (often into a method object) so the field isn't left dangling.
Gotchas
- Liskov substitution is about behavior, not just signatures:
Square extends Rectangleis the classic violation despite matching types - Mutable shared state plus method calls = order-dependent behavior; making fields
final/readonlyis the cheapest correctness lever
What ships with it
4 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.
- 7d ago Changed · +2 lines 626ee034a033
- 1mo ago First seen · 31 lines · 50 tokens per session scan A 31a9204b8e2f
oop-guide is a skill published in the GitHub repository xonovex/platform (6 stars, last pushed 4d ago), licensed MIT. It adds 50 tokens to every session and 450 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 2026-09-08.
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