What am I doing wrong with the Pocket API for Objective-C that's causing archive commands to fail?

Question

I'm really scratching my head at this one. I'm using the Pocket API to allow users to archive Pocket articles from my app, but whenever I try to do so with the below code I get this error:

Error Domain=PocketSDK Code=400 "Invalid request, please refer to API documentation" UserInfo=0xc17d3b0 {NSLocalizedDescription=Invalid request, please refer to API documentation}

Code:

          NSDictionary *arguments = @{@"action": @"archive",
                                                 @"item_id": articleID};

          [[PocketAPI sharedAPI] callAPIMethod:@"send" withHTTPMethod:PocketAPIHTTPMethodPOST arguments:arguments handler:^(PocketAPI *api, NSString *apiMethod, NSDictionary *response, NSError *error) {
                if (!error) {
                     NSLog(@"Archived article.");
                }
          }];

Exactly what part of that is incorrect? Am I not POSTing a send method to the API?

EDIT: I even changed it to have @"action" be @"actions" and to supply it the above NSDictionary, and it returns without an error but doesn't affect it on the Pocket website...

EDIT 2: Per the response of Joseph Chen I changed my code to the following:

      // Create data to pass to the Pocket API (a JSON array of actions)
      NSError *error;
      NSArray *actions = @[@{@"action": @"archive",
                                    @"item_id": articleID}];
      NSData *actionsAsJSONData = [NSJSONSerialization dataWithJSONObject:actions options:kNilOptions error:&error];
      NSString *actionsAsJSONString = [[NSString alloc] initWithData:actionsAsJSONData encoding:NSUTF8StringEncoding];

      NSDictionary *arguments = @{@"actions": actionsAsJSONString};

      [[PocketAPI sharedAPI] callAPIMethod:@"send" withHTTPMethod:PocketAPIHTTPMethodPOST arguments:arguments handler:^(PocketAPI *api, NSString *apiMethod, NSDictionary *response, NSError *error) {
            if (!error) {
                 NSLog(@"%@", response);
            }
            else {
                 NSLog(@"%@", error);
            }
      }];

Which returns:

action_results" =     (
    1
);
status = 1;

Yet when I go to the website and log in, the article I "archived" is still staring me in the face, unarchived.

Answer 1

Here's the code taken (almost) straight from my app:

NSTimeInterval timestamp = [[NSDate date] timeIntervalSince1970];
NSDictionary *arguments = @{@"actions" : @[@{@"action" : @"archive",
                                             @"item_id" : itemId,
                                             @"time" : [NSString stringWithFormat:@"%ld", (long)timestamp]}]};

[self.pocketAPI callAPIMethod:@"send"
               withHTTPMethod:PocketAPIHTTPMethodPOST
                    arguments:arguments
                      handler:^(PocketAPI *api, NSString *apiMethod, NSDictionary *response, NSError *error)
 {
     if (!error) {
         // OK
     } else {
         // handle error
     }
 }];