Before discussing whether he or she is interesting or boring, you need a brief diversion into one of the more confusing elements of Spanish grammar.

Confusingly for English speakers, Spanish has two verbs which both mean 'to be' - ser and estar, and so two ways of saying 'he/she is' es and está. (See the basic grammar).

Normally, ser is used to describe someone's personality. So you would use es 'he/she is' followed by the appropriate adjective. If Fred is a boring person, in Spanish, he would be described as es aburrido 'He is boring'.

But Ser is only used to describe the usual characteristic of a person. If Fred isn't a boring person, but happens to be bored at that particular moment, estar is used giving Está aburrido. Estar is being used to describe a transient state (estado) of affairs.

A few more things:

Simpático means more than 'nice', and there isn't a direct English translation for this. If someone is simpático they are open, charming, likeable, pleasant. Similar in a way to the old-fashioned 'He's a brick'.

Chistoso and gracioso mean 'funny' in the sense of making people laugh, as opposed to 'funny' as in 'weird' for which raro is used.

And just to be confusing sensible means 'sensitive'.

English Spanish
He/she is ... Es ...
affectionate cariñoso/a
boring aburrido/a
closed (in mind etc) cerrado/a
considerate considerado/a
dishonest tramposo/a
fault finder criticón
lazy flojo/floja
frank,open,comradely campechano/a
funny chistoso/a
funny gracioso/a
honest sincero/a
immature inmaturo/a
mature maturo/a
nice simpático/a
open (in mind etc) abierto/a
optimistic optimista
pure, chaste honesto/a
polite cortés
quiet callado/a
sensitive sensible
shy timido/a
silly tonto/a
sly astuto/a
stingy tacaño/a
thoughtful atento/a
unpleasant antipático/a


A few general example phrases illustrating the above :-

English Spanish
He/she is (a) boring (person) Es aburrido/a
He/she is strange Es una persona rara/a
You are strange (informal)! ¡Que rara eres!
They are lazy (men) Son flojos
They are lazy (women) Son flojas