It took me a minute to figure out how to test a Web Api POST method that took an array of strings so I thought I would share and save you that minute.
In Fiddler’s Composer tab, change GET to POST and enter the address of your Web.api controller (“http://yoursite.com/api/yourControllerName”).
In the Request headers tab, enter a JSON content type. (“Content-Type: application/json; charset=utf-8”)
You need more info here but Fiddler will fill the rest for you when you hit execute.
Put your JSON string array in the Request Body
Hit Execute on fiddler. Fiddler will populate the content length and post your reqeust.
Sit back and enjoy the JSONy goodness.