I keep hearing people talk about descriptive narrative as though it's something different from internal dialogue. I suppose if you're writing some kind of literary fiction from an omniscient POV, it might be. But for the most part--especially in children's and YA fiction--it is the same thing.
Interiority and description are the same. It's all in the POV voice. It's all about what the POV character is thinking. Sometimes they're thinking about their feelings and motivations, sometimes they're thinking about what they're seeing/hearing etc.
All of it needs to be written from the mindset of the POV character.
Remember this poem by Wordsworth?
I wandered lonely as a cloud
That floats on high o'er vales and hills,
When all at once I saw a crowd,
A host, of golden daffodils;
It's easy to try too hard to write a snarky narrative voice, but then when it comes time for description, wax into an eloquent Dickensesque voice.
It should be all the same voice.
All writers struggle with this, so practice and always keep it in mind.