Cataloguing
Writing structured descriptions of primary sources is referred to as cataloguing or creating documentation. These data (whether made in digital form or, as was, in physical forms such as card catalogues) help someone new to the source understand some basic information about it: what it is, when it was created, by whom, and how to understand it in the context of other sources.
Increasingly, cataloguing is seen as a reflexive practice. That is, whilst once professional cataloguers saw their task as to create objective statements about the objects their were cataloguing, since the postmodern turn in archival science (key figures in which were Terry Cook and Joan M. Schwartz, see “Archives, Records, and Power: From (Postmodern) Theory to (Archival) Performance,” Archival Science 2:3 (2002) the impossibility of creating objective statements has been widely recognised. In its place has emerged cataloguing practice that recognises its positionality (that is, the cataloguer is a person speaking in a particular place, at a particular time, from a particular perspective and set of relations) and seeks to make statements that are reflexively grounded in that positionality.
As students building this archive, your task therefore is not to create 'truth' in the documentation you produce, but to make statements about primary sources that a) you can justify and b) recognise your position as an interlocutor between the present and the past(s) you are describing.
If feel totally stuck, consider the advice on pages 26-27 of "Preserving Communities' Heritage: A Workbook for Heritage Capturers": imagine you are describing the primary source to someone with poor eyesight, focus on the details you imagine they might find interesting, and build you reflections of the significance of the source from there.
As visitors to this archive, your task is not to consider the documentation you find as 'truthful' statements about the past, but to read those statements about primary sources as a) statements that the cataloguer understood as justifiable and b) positionally inscribed interlocutions between the present and the past(s) being described.