What skills cost

Every installed skill's name and description sit in context on every message, whether it's used or not. Tools cap that list: Claude Code at 1% of the model's context window and Codex at 2% (their documentation, October 2026). When the list overflows, descriptions are dropped and those skills can't be matched to a request any more, so they go quiet. This measures how close a person is to that.

npx -y @thenavidm/skill-builder@latest tokens <skill-or-plugin>

(skill-builder tokens <skill-or-plugin> where it's installed globally.)

Reading the result

• every message: the skill's name and description. This is the cost that adds up across everything they have installed.
• when it runs: its SKILL.md body, paid only when it fires.
• files it can load: references it reads only when a step needs them.
• The plugin's share of each tool's budget on a 200,000-token model and on a 1,000,000-token one. Over 100% means this plugin alone overflows the list on that model.

The numbers are estimates at about 3 characters a token, measured against Claude Code's own counts (19 October 2026). Say so when you quote them.

When it's too heavy

In order of how much each saves:

1. Shorten descriptions. What it does and when, in about 300 characters. Lists of keywords cost the most and help the least.
2. Fewer skills that start on their own. A plugin's entry skill can route to the rest; skills that only run when asked (disable-model-invocation: true) can leave the list in Claude Code and Cursor.
3. Merge skills that always run together.
4. Move detail out of SKILL.md into references, to cut the cost when it runs.

After each change, run tokens again and show the before and after. If they also have evals/triggers.json, run skill-builder trigger to confirm the shorter descriptions still fire.