Do you type the same thing at the beginning of a conversation with Claude more than three times? That's already a skill.
A folder with a single SKILL.md file in ~/.claude/skills/ — and Claude picks it up automatically.
The most important part is the trigger description: exact phrases for when to use it, and explicitly — when not to. A weak trigger = the skill never activates.
Need calculations — add a scripts/ folder.
One rule: one script — one task.
