Unable to update message through the API using C#

With the API I have been able to read folders, messages, attachments, but I am unable to get the updatemessage function to work.

Here is my code:

var restClient = new RestClient(" https://mail.zoho.com/api/accounts/<accountid>/updatemessage");

var request = new RestRequest(Method.PUT);

request.AddParameter("authtoken", "<token>");

request.AddParameter("mode", "archiveMails");

request.AddParameter("messageId", "[\"<messageid>\"]");

var response = restClient.Execute(request);

This gives the error code JSON_PARSE_ERROR

Any guidance would be much appreciated, as I have searched all over google and tried various things to no avail. Thanks!