In what way does Prospero in The Tempest, function as a playwright?
Basically, from the time he is on the island until the end when he reveals what he's done, he controls the entire play and many of the characters' actions. Using magic, he causes the storm that strands Alonso and Antonio on the island. Prospero directly manipulates Ferdinand and Miranda but relies on Ariel to deal with Gonzalo, Antonio, Sebastian, Alonso, Caliban, Trinculo and Stephano. So, in this sense, being more removed from the action and yet controlling it, he is most like a playwright. By controlling the action, he is writing the play itself.
With so many references between magic and writing, I think there is an obvious connection between Prospero and Shakespeare. Being that it may have been Shakespeare's last play, it has special significance.
I'll break my staff,
Bury it certain fathoms in the earth,
And deeper than did ever plummet sound,
I'll drown my book (V.i, Prospero).
And the epilogue:
With the help of your good hands:
Gentle breath of yours my sails,
Must fill, or else my project fails,
Which was to please.
I liked to think "help of your good hands" was applause at the end of the play, "gentle breath" cheers or well wishes. His "project" was to entertain/enlighten.