With the colloquial pattern …就是了 we can emphasize that the action is completed, and that there is nothing more to do.
We should state it at the end of a sentence, usually after an imperative statement.
Take your passport and that's it
nǐ dài hùzhào jiù shì le
Just give him five dollars, please!
qǐng gěi tā wǔ kuài jiù shì le
Don't worry, just trust me
bú yòng dānxīn, xiāngxìn wǒ jiù shì le
The patterns …就行了 and …就可以了 have a similar meaning.
In the pattern …就行了, we can omit 了 and just say …就行.
Just wearing jeans and a T-shirt will be fine
niúzǎikù hé T-xù jiù kěyǐ le
If the chicken is not too big, you can simply split it in half