The adjective has 3 meanings:
Meaning #1:
in keeping
Synonyms: accordant, agreeable, conformable, consonant, in accord, concordant
Meaning #2:
united by being of the same opinion
Synonym: agreed
Meaning #3:
being of the same opinion
Synonyms: agreeing, concordant, concurring, of the same mind
The adverb in agreement has one meaning:
Meaning #1:
with a common plan
Synonyms: in concert, together
