Comparison
Claude Code skills vs custom instructions / CLAUDE.md
Custom instructions (like a CLAUDE.md) set global behavior for every task. A skill is scoped, reusable know-how the agent invokes when relevant — with its own references and test. Use both: instructions for defaults, skills for specific workflows.
Quick answer
Claude Code skills: A skill is a self-contained, invocable workflow (SKILL.md + references + test) the agent uses when the task calls for it. Custom instructions: Custom instructions are always-on guidance that shapes every response in a project.
| Claude Code skills | Custom instructions | |
|---|---|---|
| Scope | Per-workflow, invoked on demand | Global, always applied |
| Carries references & test | Yes | No |
| Reusable across projects | Yes — portable folder | Per-project file |
| Best for | Specific multi-step processes | Defaults, tone, house rules |
| Shareable / sellable | Yes | Usually not |
Use Claude Code skills when
- You have a specific process to encode and reuse
- You want references and a test bundled in
Use Custom instructions when
- You want to set global defaults and conventions
The verdict
Set your defaults in custom instructions; package repeatable workflows as skills. They stack.
Build the skill for your side of this
Loreto turns any source into a Claude Code skill — package, CLI + MCP, or both.