Preheat oven to 350 degrees F (175 degrees C). Lightly grease a medium baking dish.
Arrange the chicken in the baking dish, cover, and bake 25 minutes in the preheated oven, until juices run clear.
Remove from heat, cool, and shred.
In a large bowl, mix the shredded chicken, celery, tarragon, parsley, mayonnaise, raisins, and onion. Refrigerate 1 hour, or until chilled, before serving.