Claude Code puts a short list of your skills into every conversation: each skill's name plus its description. Claude uses the description to decide which skill fits your request.
That list has a budget: 1% of the model's context window (Claude Code docs, "Skill descriptions are cut short").
When your skills don't fit, Claude Code keeps every name but drops descriptions, starting with the skills you use least.
A skill without a description has no words Claude can match against, so it only runs when you type /its-name.
My setup on 30 Sep 2026: 118 skills, 59,112 characters of descriptions, a 30,000 character budget.