The test
A success measure is adequate when two people who disagree about whether the project worked can read it and reach the same answer. If they cannot, it is not a measure. It is a mood.
The three requirements are specificity, a named source, and a date. Illustrative example: “Increase qualified enquiries from the faculty site from a baseline of 40 per month to 65 per month by 31 March, measured in Google Analytics 4.” Every element there is contestable in advance and settled afterwards.