How does one know that it's "tell me" rather than "I should tell"? Context?
'I should tell' would need an object, whereas 'tell me' is a complete sentence with verb, subject, object since it's a command
According to Wilson's 'Simplified Swahili', there are three verbs that always must be used with an object infix (and it must be from the m- wa- class):
Kuambia: to tell, kuita: to call and kupa: to give to.