The AP Stylebook prescribes its use by wire reporters (in a "keyword slugline") as follows: "The keyword or slug (sometimes more than one word) clearly indicates the content of the story." Sometimes a slug also contains code information that tells editors specific information about the story — for example, the letters "AM" at the beginning of a slug on a wire story tell editors that the story is meant for morning papers, while the letters "CX" indicate that the story is a correction to an earlier story.
The AP Stylebook advocates for its application by wire reporters (in a "keyword slugline") in the following way: "A keyword or slug (which can comprise multiple words) clearly defines the article's subject." Occasionally, a slug also contains coding details that inform editors about the story — such as the letters "AM" at the beginning of a wire story slug, signifying it's intended for morning publications, and "CX" denoting a correction to an earlier piece.