The starting point for any issue relating to an agenda is your standing orders but if you have adopted the model set, you will see certain elements written in bold type and these are sections based upon statutory provisions so cannot be amended. The requirements for the business to be transacted to be included on the agenda is contained within the Local Government Act 1972, Sch 12, paras 10(2)(b) and para 26(2)(b). If a matter to be discussed is confidential, then the agenda item may be vague so as not to give too much detail to the public. For example, a staff disciplinary matter might be referred to as "staffing matter".
The subject of publication of reports or supporting documents has been referred to several times in previous threads. In brief, if a report exists, it should (a) be sent to councillors before the meeting and (b) published on your website along with the agenda. Reports on confidential matters may well be not published legitimately on the grounds they are confidential (assuming that they are genuinely confidential for good reason) but if in existence it follows they should be sent to councillors albeit possibly with the caveat that they should not be disclosed outside of the council.