In the following sentence:
図書館へ行くつもりなんだ
What is なんだ from the grammar point of view?
In the following sentence:
図書館へ行くつもりなんだ
What is なんだ from the grammar point of view?
I guess I was right, so I'll offer it as an answer.
According to Daijirin (look at the bottom of the link) it is a shortened form of the 連語 なのだ
.