The Search Criteria parameter in the Add Locations and Calculate Locations tools controls the network sources used when locating inputs and how inputs are located. Historically, the tools supported locating inputs on the middle or end of a network edge using the snap type options MIDDLE, END, and MIDDLE_END. These options are not useful for modern workflows and are deprecated. Inputs are always located on the closest point of the closest locatable network source.
Do not use the MIDDLE, END, or MIDDLE_END snap type. Use SHAPE to specify that inputs can be located on the designated network source and NONE otherwise.