# Solid Principles > SOLID principles for object-oriented design. Use when reviewing code quality, refactoring, designing classes or interfaces, or discussing architecture patterns. Use when this capability is needed. - Skill: `tomevault-io/solid-principles-3` (Agent Skill, multi-file: 2 files) - Install (CLI): `npx skillmds@latest add tomevault-io/solid-principles-3` - Raw SKILL.md: https://api.skillmd.com/api/skills/tomevault-io/solid-principles-3/raw - Safety review: pending - Works with: Claude Code, Claude.ai, OpenAI Codex - Category: Coding & Dev Tools - Author: tomevault-io (https://skillmd.com/u/tomevault-io) - Updated: 2026-09-17 - Page: https://skillmd.com/skills/tomevault-io/solid-principles-3 --- # SOLID Principles This skill provides universal SOLID principles guidelines for object-oriented code quality. See @REFERENCE.md for detailed documentation. ## Quick Reference - **S**RP: One reason to change per class - **O**CP: Extend via interfaces, don't modify existing - **L**SP: Subtypes substitutable for base types - **I**SP: Small interfaces (< 5 methods) - **D**IP: Depend on abstractions, not implementations --- > Converted and distributed by [TomeVault](https://tomevault.io/claim/thebeardedbearsas) — claim your Tome and manage your conversions.