Friendly staff.
( Friendly ( staff . ) )
(ROOT (NP (JJ Friendly) (NN staff) (. .)))
The staff is friendly only when you give them tips.
( ( The staff ) ( ( ( ( is friendly ) only ) ( when ( you ( ( give them ) tips ) ) ) ) . ) )
(ROOT (S (NP (DT The) (NN staff)) (VP (VBZ is) (ADJP (JJ friendly)) (ADVP (RB only)) (SBAR (WHADVP (WRB when)) (S (NP (PRP you)) (VP (VBP give) (NP (PRP them)) (NP (NNS tips)))))) (. .)))