'Transparency' is frequently invoked when describing assessment criteria in higher education. However, there are limitations to the metaphor: 'transparent' representations give the illusion that everything can (and should) be explicated, and that students are 'seeing through' to the educators' expectations. Drawing from sociomaterial perspectives on standards, an argument is made for a different way of conceptualising assessment criteria. 'Invitational' enactments offer an alternative metaphor, one which intentionally promotes student learning. Three propositions frame potential use of this metaphor: (1) assessment criteria promote learning when they invite students into a 'productive space'; (2) assessment criteria coordinate sustained learning by inviting multiple enactments across tasks; (3) assessment criteria develop sophisticated ways of knowing by inviting student reflection. Drawing from both metaphors, teachers can design assessment materials -- particularly rubrics, task descriptions and exemplars -- which convey their intentions while also prompting students to develop their own ways of working and learning.