One trigger line per skill lifted Claude Code skill recall to 67%

A team running about 20 Claude Code skills measured how often each one actually fired when it should have. More than half the prompts that should have triggered a skill triggered none, according to a thread on r/ClaudeAI laying out the test.

The fix was cheap. Adding one line to each skill, something like "Always invoke for .proto files" tied to a trigger unique to that skill, such as a file extension, raised recall from 46% to 67.3% while precision held around 0.96. Skills with a narrow, ownable trigger jumped the most.

One skill got worse. Their generic "review" skill had nothing unique to anchor on, no file type or keyword no other skill also claimed, so the added line didn't help and recall dipped slightly. A trigger only works when it points at something exclusive to that skill.

Their detector only caught Claude's own Skill tool call. Codex and Antigravity read SKILL.md straight off disk instead of calling a tool, so the same test run against those agents would undercount however many times they used a skill without it showing up as a call.

I've got a handful of skills in my own setup I've never actually confirmed are firing. This is the cheapest test I know of to find out, and cheaper still to fix once you know which ones are dead weight.