Each entity (i.e. candidate generator, mapping, prior) in p-search can have a number of configuration arguments. These are divided into two types: inputs and options. Inputs are arguments that must be defined for the entity to function properly while options are optional and set up modified behavior. You will notice the two type of arguments as two sections in the transient menu. Some inputs (i.e. required arguments) will have defaults. If a default is not provided however, you will always be prompted for its value for it not to be blank.