No, that’s not possible. For portals with a significant number of contacts, returning all of them in a single request would result in timeouts and/or huge response sizes.
The results of the get all contacts endpoint (the one you’re using) are paginated, meaning that you’ll only get 100 contacts at a time. In order to pull more, you’ll need to use the has-more field to determine if there are more contacts and the vid-offset field to pull the next page of contacts. This developer doc has more info on this: