事(こと)だShould, Ought

As a sentence ending particle, こと has two primary functions. These are as follows:

願望(がんぼう)や軽(かる)い命令(めいれい)を表(あらわ)す - Highlighting a desire or weak command.

感嘆(かんたん)や疑問(ぎもん)を表(あらわ)す - Highlighting astonishment or doubt.

We will focus on the first meaning in this grammar point, as the 'astonishment' nuance is not as commonly used in modern Japanese, and is primarily used only by women.

At the end of a sentence, こと will be paired with the dictionary (or ない) form of a verb, to highlight a particular action that either should, or should not occur. It is usually grouped with the auxiliary verb だ, although this is not always the case. This construction is most often translated as 'should/should not (A)', or 'ought to/not (A)'.

Caution

This use of こと implies a certain level of 'authority', and is therefore regularly used in relation to set rules and expectations (can very frequently be seen on signs in shops/parks, etc). Due to this, it should not be used when giving 'general' advice, especially to people of higher status.