Methodology
The method is fully public; only the questions are private. That is what makes "tests private" credible rather than suspicious.
How grading works
Each suite is a set of graded tasks with a fixed scoring method - programmatic checks or a pinned LLM judge - run several times per agent for stability.
Capability rolls up to a letter grade per suite via published grade bands, alongside plan cost, task time, and reliability. Grades are comparable within a suite version only.