口先

mere words, lip service

k ɯ̟ t͡ɕ i s a̠ kʲ i
mouth + ahead, the future
noun Rare #42,102
mere words, lip service Often refers to words spoken without sincere action or commitment.
JA: 口先だけで約束を守らない人は信用できない。
EN: You can't trust people who make promises but don't keep them.

口先ばかりだ

All talk and no action.

— アメリカン・ギャングスター (2007)

ただ口先ばかりで何の役にも立たない

Empty words alone are of no use.

口先だけでなくもっと実行が必要だ

You need to do more than just talk; you need to take action.

口先よりも実践大事なんだよ

Actions speak louder than words.