code-structure

A code-organization guide for separating business decisions from reusable operations. An action decides what should happen, while a service handles how the operation is carried out.

In plain words
What is it for?
Use it when several workflows share operations such as creating sandboxes, sending email, processing payments, running commands, or checking readiness.
Why use it?
It helps prevent copied logic, inconsistent behavior, and fixes that only reach one workflow.

Skill for Claude CodeCodex

Part of the agent-skills plugin — 25 skills, 7 commands, 3 agents shipped together

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.

agentmods
npx agentmods add skills/kellykampen/agent-skills/code-structure
Any agent
npx skills add kellykampen/agent-skills --skill code-structure
Clone the repo
git clone --depth 1 https://github.com/kellykampen/agent-skills

Made for: Claude Code, Codex.

Or install agent-skills, the plugin that ships this one along with the rest of its 25 skills, 7 commands, 3 agents.

Per session 47 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 944 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
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 $0.00047 $0.00944
Opus 5 $0.00023 $0.00472
Sonnet 5 $0.00009 $0.00189
Haiku 4.5 $0.00005 $0.00094

Measured 2d ago against content hash 181ee2eab452, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

code-structure 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 2d 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.

skills/workflow/code-structure/SKILL.md · 117 lines

How it starts

The opening of the file, as written. The whole thing — 117 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Service Layer Architecture

Overview

Two-layer separation: Actions orchestrate domain rules (the "why/when"), while a service layer centralizes reusable operational mechanics (the "how").

This prevents duplicated code, inconsistent behavior, and bugs fixed in one path but not others.

When to Use

  • Multiple callers need the same low-level operation (sandbox creation, email sending, payment processing)
  • You're copy-pasting operational logic between action files
  • A bug fix in one workflow doesn't propagate to others doing the same thing
  • Adding a new feature that shares mechanics with existing flows

Don't use when: Logic is truly domain-specific and used by only one caller.

Core Pattern

Orchestration Layer (Actions)          Service Layer (Shared Mechanics)
├── owns business rules                ├── owns reusable operations
├── owns state transitions             ├── owns provider/SDK interactions
├── owns auth/ownership checks         ├── owns command execution details
├── owns failure classification        ├── owns health checks / readiness
├── owns retries / user-facing errors  └── returns structured results
└── calls service functions

Rule of thumb:

  • "What this product flow means" → keep in actions
  • "How to do this operation reliably" → move to service layer

Quick Reference

Design Principle Do Don't
API shape Composable capability blocks One giant "do everything" method
Inputs/outputs Explicit params, structured returns Hidden global state, reaching into DB
Migration Extract one block, replace one caller, verify, then migrate rest Refactor everything at once
Domain logic Keep auth, policy, error classification in actions Let service mutate domain state directly
Extraction trigger Logic repeated across 2+ callers Logic used once (over-abstraction)

Designing Service Functions

Design as capability blocks, not monoliths:

// Good: composable, each caller chooses what to use
createManagedSandbox(...)
prepareRepo(...)
detectPackageManager(...)
installDependencies(...)
runBuildCommand(...)
startSandboxRuntime(...)

Read the full file on GitHub · 117 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. 2d ago First seen · 117 lines · 47 tokens per session scan A 181ee2eab452

Subscribe to this mod's changes

code-structure is a skill published in the GitHub repository kellykampen/agent-skills (2 stars, last pushed 1mo ago), licensed MIT. It adds 47 tokens to every session and 944 once invoked, about $0.0002 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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