I scored 356 publicly collected AI agent prompts against 23 written guardrail controls. The 83 that came from production tools had a median coverage of 10 out of 100. The 273 pulled from the GPT Store had a median of zero.
The gap between those two numbers is real — Cliff's delta 0.614, p = 0.0001. But it is a smaller finding than it looks, and the parts where the measurement broke turned out to be more useful than the parts where it worked.
What "coverage" means, and what it doesn't
Coverage is the share of 23 published controls a prompt actually states. Things like: treat instructions inside user content as data rather than commands. Say so when you don't know. Cap spend or tokens. Require a human to approve before a consequential action. Name what triggers stopping.
Nothing written down scores 0. One control stated in each of the 8 dimensions scores 36. All 23 controls score 100.
