Why Does It Need to Be a Wise Woman?

In the first story, Joab sent to Ticoa and brought from there a wise woman. So if he's like giving her all of the instructions, right, why does it need to be a wise woman? Why couldn't it just be any old woman? That's a good question. But apparently he knows that there is a wise woman specifically who lives in Ticoa,. Otherwise it would say he cast about for someone who looked like she could be a good actress. He either knows of a specific woman or a role that is held by a woman in TicoA. And he goes and gets specifically her.