Riptide is a magical sword, also known as Anaklusmos, that takes the form of a ballpoint pen. Percy can only use it as a sword when he needs it, as it transforms back into a pen when he isn't actively fighting.
Here's how he uses Riptide:
* Uncapping: To turn the pen into a sword, Percy simply uncaps it.
* Combat: He uses the sword to fight monsters, titans, and other enemies, using its sharpness, durability, and magic to his advantage.
* Transformation: When he's done fighting, the sword automatically transforms back into a pen, so it's not a constant threat or a giveaway of his abilities.
So, while Percy could technically scratch something with Riptide in its pen form, he wouldn't use it to write. He has a perfectly normal pen for that!