Yeah, that means that the body of that file will not be injected into the context on startup.

I had thought that once the skill is selected the whole file would be read, but it looks like that's not the case: https://github.com/openai/codex/blob/ad7b9d63c326d5c92049abd...

  1) After deciding to use a skill, open its `SKILL.md`. Read only enough to follow the workflow.

So you could have a skill file that's thousands of lines long but if the first part of the file provides an outline Codex may stop reading at that point. Maybe you could have a skill that says "see migrations section further down if you need to alter the database table schema" or similar.