Agent-Skills.md

Agent Skills: Fundamental Coding Principles

Fundamental coding principles (DRY, KISS, YAGNI, SOLID, HHH). Use when starting any development task, evaluating implementation approaches, or reviewing code quality. Always active as foundation for all development decisions.

UncategorizedID: tianjianjiang/smith/smith-principles

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smith-principles/SKILL.md

Skill Metadata

Name
smith-principles
Description
Fundamental coding principles (DRY, KISS, YAGNI, SOLID). Always active. Use when starting a development task, choosing an approach, or reviewing code quality.

Fundamental Coding Principles

Prerequisites: None Sources: references/SOURCES.md

Critical Rules

  • Apply DRY before adding features
    • DRY means one representation per piece of knowledge, not per code text; look-alike code can be a coincidence
  • Apply KISS: choose the simplest solution
    • Simplest in the SINE sense below, not the most familiar
  • Apply YAGNI: defer unneeded implementation
    • It presumes code that stays easy to change; it does not forbid making code easy to change or excuse half-done work
  • One reason to change per module (Single Responsibility)
    • A reason is a person or role who asks for changes, not "does one thing"
  • Open for extension, closed for modification (Open/Closed)
  • Subtypes substitutable for base types (Liskov Substitution)
    • Substitutable in behavior, not only in signature or by inheritance
  • Many specific interfaces over one general (Interface Segregation)
  • Depend on abstractions, not concretions (Dependency Inversion)
  • Complete coverage without overlap (MECE)
    • Exhaustive of a stated whole; name the boundary or an "other" group
  • Fewest assumptions (Occam's Razor)
    • Among options that explain the evidence equally well; it does not claim the simpler option is more likely true
    • Before removing something, state its purpose and why that purpose no longer holds (Chesterton's fence)
  • Say what a thing is not when a positive claim would overreach (via negativa)
    • It is not deletion; deletion belongs to Occam's Razor
  • Simple is not easy (SINE): simple means not entangled; easy means familiar or near at hand, and simplicity takes effort

Related

  • @smith-standards/SKILL.md - Universal coding standards
  • @smith-guidance/SKILL.md - AI agent behavior (safety rules, anti-sycophancy)

Before You Finish

Before implementing: Check for existing abstractions (DRY), choose simplest approach (KISS), confirm feature is needed now (YAGNI), verify SOLID principles, verify MECE, Occam's Razor, and SINE