I am trying to test post comment with the following URL

    https://api.stackexchange.com/2.1/posts/10305691/comments/add?key=HIDDEN&access_token=HIDDEN&site=stackoverflow&preview=true&body=text123456789123&client_id=HIDDEN

**Request Headers**

    Accept: */*
    Content-Type: application/x-www-form-urlencoded; charset=UTF-8 
    Accept-Encoding: gzip,deflate,sdch
    Accept-Language: en-US,en;q=0.8

I get the following response:  

    HTTP Error: 400 Bad Request

    {
       "error_id": 500,
       "error_name": "internal_error",
       "error_message": "this error has been logged"
    }

But the same POST request works when run from the console at the [API doc][1].

So I used firebug to copy the full URL with parameters that was sent by the test console provided for /posts{id}/comments/add. I also copied the full list of request headers from firebug and tried using a REST client to test the same but I got the same error response as above.

Is there anything I am missing here?


  [1]: https://api.stackexchange.com/docs/create-comment