That's an interesting exercise. I put 'It’s a rounded toy yellow old small metal cute car.' into my grammar checker and it didn't pick anything up and I put it into ChatGPT without asking anything and it replied -

The description you provided can be organized to better adhere to the typical order of adjectives in English. The usual sequence is:

Quantity (a/an, some, two)

Opinion (cute, lovely, charming)

Size (small, large, tiny)

Age (old, new, ancient)

Shape (rounded, square, oval)

Color (yellow, red, blue)

Origin (French, American, Asian)

Material (metal, plastic, wooden)

Purpose (toy, racing, cooking)

Applying this order to your description:

A cute small old rounded yellow metal toy car.