Go to writesonic Choose Chatsonic (Click the Button next to Instruction, to open the menu) Under Language select PHP. To make it easier, insert something in X API… . Choose the params you need on the left. On the right side you may recognize some things you can see in the Shortcut.

You habe to edit the dictionary (the action with the URL), because keys and values are different here. After that delete everything after this URL-Dictionary-Thing and set a text from url contents action and a Show results action. Run the shortcut. You should get an answer. Delete the unnecessary parts with replace text actions. Put the Show results Action to the end of the shortcut or set a speak text action.

This worked for me.