object-design-skill

object-design-skill is a skill for OpenCode from darellchua2/opencode-config-template. It costs 28 tokens per session (3,458 once invoked), scanned A, original, Apache-2.0.

A language-independent guide to designing object-oriented code with clear responsibilities and protected internal state. It covers concepts such as value objects, entities, aggregates, and composition.

In plain words
What is it for?
Use it when designing or refactoring classes, modeling business concepts, choosing between values and entities, and improving encapsulation.
Why use it?
It helps prevent classes from becoming unclear, tightly coupled, or responsible for too many unrelated tasks.

Skill for OpenCode

Written for OpenCode: installed under .opencode/. Also seen: mentions OpenCode.

Good fit Use it when designing or refactoring classes, modeling business concepts, choosing between values and entities, and improving encapsulation.

Compare 6 skills from other repositories ↓
Install with agentmods
npx agentmods add skills/darellchua2/opencode-config-template/object-design-skill
Install

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.

Any agent
npx skills add darellchua2/opencode-config-template --skill object-design-skill
Clone the repo
git clone --depth 1 https://github.com/darellchua2/opencode-config-template

Made for: OpenCode.

Wrote 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.

agentmods badge for object-design-skill

README.md
[![agentmods](https://agentmods.dev/badge/skills/darellchua2/opencode-config-template/object-design-skill.svg)](https://agentmods.dev/skills/darellchua2/opencode-config-template/object-design-skill)
Your own site
<a href="https://agentmods.dev/skills/darellchua2/opencode-config-template/object-design-skill"><img src="https://agentmods.dev/badge/skills/darellchua2/opencode-config-template/object-design-skill.svg" alt="Measured on agentmods" height="20"></a>
Per session 28 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 3,458 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. A grade says what 26 rules found in the file — not that it is safe. Third-party audits
  • NVIDIA SkillSpector warn 7 Sept 2026
SkillSpector: 1 finding, up to high

These are SkillSpector’s own severities. On a checked sample its high-severity flags on skills were ~96% false positives — a documented command, a public API, a “never do X” rule — so we show them as a caution to read, not a verdict. Why →

  • high Memory Poisoning · line 211
    Skill manipulates agent memory, state, or stored context. Memory corruption can alter personality, override safety rules, or cause unpredictable behavior.
    Fix: Protect agent memory and state from modification by untrusted content. Use read-only memory for critical instructions and validate all state changes.
How audits are shown
Origin original No closer match found in the catalogue.
Token cost

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.

ModelPer sessionOnce invoked
Fable 5.1 $0.00028 $0.03458
Opus 5 $0.00014 $0.01729
Sonnet 5 $0.00006 $0.00692
Haiku 4.5 $0.00003 $0.00346

Measured 4d ago against content hash fed5d3997355, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-07, from the pricing page.

Security

Grade A, and why

object-design-skill 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 4d 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.

opencode_app/.opencode/skills/object-design-skill/SKILL.md · 567 lines

How it starts

The opening of the file, as written. The whole thing — 567 lines — stays where its author put it; the contents beside it link to each section on GitHub.

What I do

I help you design objects with clear responsibilities and proper encapsulation:

  1. Identify Object Stereotypes: Classify objects as Information Holders, Structurers, Service Providers, Coordinators, Controllers, or Interfacers
  2. Design Value Objects: Create immutable objects for domain primitives (IDs, emails, money)
  3. Design Entities: Create objects with identity that persist through changes
  4. Apply Tell Don't Ask: Command objects instead of interrogating them
  5. Design Aggregates: Create clusters of objects with consistency boundaries
  6. Apply Composition over Inheritance: Prefer composing objects over extending classes

When to use me

Use this skill when:

  • Designing new classes or modules
  • Refactoring classes that have unclear responsibilities
  • Creating domain models for business concepts
  • Deciding between value objects and entities
  • Implementing domain-driven design patterns
  • Reducing coupling between objects
  • Improving encapsulation and information hiding

Prerequisites

  • Understanding of object-oriented programming
  • Knowledge of the business domain
  • Familiarity with interfaces and abstractions
  • Understanding of immutability concepts

Responsibility-Driven Design (RDD)

The key insight: Objects are defined by their responsibilities, not their data.

Finding Objects

Start with:

  1. Nouns in requirements → candidate objects
  2. Verbs → candidate methods/behaviors
  3. Domain concepts → value objects

Finding Responsibilities

Each object should answer:

  • What does this object know?
  • What does this object do?
  • What does this object decide?

Object Stereotypes

Every class fits one (or maybe two) stereotypes:

Stereotype Purpose Example
Information Holder Knows things, holds data User, Product, Address
Structurer Maintains relationships OrderItems, UserGroup
Service Provider Performs work PaymentProcessor, EmailSender
Coordinator Orchestrates workflow OrderFulfillmentService
Controller Makes decisions, delegates CheckoutController
Interfacer Transforms between systems UserAPIAdapter, DatabaseMapper

Read the full file on GitHub · 567 lines

Changes

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.

  1. 4d ago First seen · 567 lines · 28 tokens per session scan A fed5d3997355

Subscribe to this mod's changes

object-design-skill is a skill published in the GitHub repository darellchua2/opencode-config-template (6 stars, last pushed yesterday), licensed Apache-2.0. It adds 28 tokens to every session and 3,458 once invoked, about $0.0001 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 2026-09-03.

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