De vs Des
How come it’s DE petits outils and not DES petits outils
According to Monique L'Huillier in "Advanced French Grammar", des becomes d' or de when the noun is preceded by an adjective.
Thus it would be 'des outils' but 'de petits outils'.
In English, one would say 'an orange' but 'a small orange', so the presence of an adjective affects the choice of article there, too.
Now, do you know why in this case the adjective goes in front of the noun rather than after it?
You would say 'de petits outils' but 'des outils jaunes'.
It’s de petit outils because the adjective is apart of the BANGS exception and when the adjective is size related it goes in front of the noun monsieur