You can (and probably should) use the XML API to create many VLANs in one go. Here's some sample code that will do this for you. All you need is Perl and a text file that contains  vlan_name,vlan_number  lines.

#!/usr/bin/perl
#
# UCS API Perl script to create contiguous range of N VLANs
#
# cpaggen at cisco dot com
#
# input file format is
#   vlan_name,number
# eg:
#   foo,666
#   bar,667
#   foobar,800

use strict;
use warnings;
use Getopt::Long;
use LWP::UserAgent;
use HTTP::Request::Common;

$|++;

GetOptions( "ip=s"=>\my $ip,
            "user=s"=>\my $user,
            "password=s"=>\my $password,
            "f=s"=>\my $configfile,
        "help!"=> \my $help) or die "Incorrect usage - type --help for guidelines\n";

if ((!defined($configfile) || !defined($ip) || !defined($password) || !defined($user)) || ($help) )
{
    die ("createvlans -ip -user -password -f \n");
}

my $browser = LWP::UserAgent->new(agent => 'perl post');
my $xmlcmd = "";

my $url = 'http://'.$ip.'/nuova';
my $xml_header = "";
my $request = HTTP::Request->new(POST => $url);
$request->content_type("text/xml; charset=utf-8");
$request->content($xmlcmd);

my $response = $browser->request($request);
if ($response->content =~ m/errorDescr=\"([a-zA-Z0-9_\-\. ]+)\".*/)
{
    die ("Login failure: ".$1."\n");
}

# cookie format: outCookie="1263997145/efd499ed-cd2e-4128-8de7-16598d80d8c9"

$response->content =~ m/outCookie=\"(\d{10}\/\w{8}\-\w{4}\-\w{4}\-\w{4}\-\w{12})\".*/;
my $ucscookie = $1;
print ("Login successful - obtained UCS cookie ".$ucscookie."\n");

open (my $in, $configfile);
while (<$in>)
{
  chomp;
  my @vlan=split(",",$_);
  print ("Creating vlan ".$vlan[0]." (".$vlan[1].")\n");
  my $xmlcmd = "
                  
                   
                    
                    
                   
                         
                        ";
        $request->content($xmlcmd);
        $response = $browser->request($request);
        if ($response->content =~ m/status=\"created\"/)
    {
      print (" ... success\n");
    } else
          {
            print (" ... error\n");
      }
}