Tip: plugin eval's no-plugin baseline is the number that matters, not the score
Claude Code Docs·high signal
Every case runs three times with the plugin loaded and three times with no plugin at all, producing `WITH`, `W/OUT` and a delta. A case scoring 1.0 in both arms means the plugin contributed nothing. The documented failure signature for a skill that never fires is a delta near zero with the case's `tool_used: Skill` grader failing, which reads as a pass if you only look at the absolute score.