Write when, not just what
The specification asks the description to say what the skill does and when to use it, with keywords an agent can match against a task. Compare a description that reads as a title with one that names the trigger: file types, tool names, the words a person would use asking for the work. The second is matchable, the first is decoration.
Check the name and directory first
Before rewriting anything, confirm that the name in frontmatter matches the parent directory exactly, and that the name obeys the format: 1 to 64 characters, lowercase letters, digits and hyphens, no leading, trailing or repeated hyphens. A mismatch here produces exactly the same symptom as a bad description, which is silence.
Then look for a neighbour that already claimed the task
If two installed skills describe overlapping territory, one of them will usually win every time and the other will look broken. Narrow the descriptions until each names a distinct trigger, or merge them. This is worth checking before you conclude the format is unreliable.