Maybe this would be more helpful:
define( 'API_ERROR_INVALID_ARGS', 99 );
define( 'API_ERROR_INVALID_IP_TYPE', 801 );
define( 'API_ERROR_NO_SHARED_IPS', 802 );
define( 'API_ERROR_NO_STATIC_IPS', 803 );
define( 'API_ERROR_UNKNOWN_IP_RULE', 804 );
define( 'API_ERROR_ZONE_EXISTS' , 901 );
define( 'API_ERROR_DOMAIN_EXISTS', 902 );
define( 'API_ERROR_EMPTY_EMAIL', 903 );
define( 'API_ERROR_EMPTY_DOMAIN', 904 );
define( 'API_ERROR_EMPTY_IP', 905 );
define( 'API_ERROR_EMPTY_PASSWORD', 906 );
define( 'API_ERROR_INVALID_IP', 908 );
define( 'API_ERROR_IP_IN_USE', 909 );
define( 'API_ERROR_NO_IPS_AVAILABLE', 910 );
define( 'API_ERROR_SUBDOMAIN_EXISTS', 911 );
define( 'API_ERROR_INVALID_DOMAIN', 912 );
define( 'API_ERROR_INVALID_EMAIL', 913 );
define( 'API_ERROR_UNKNOWN_PACKAGE', 914 );
define( 'API_ERROR_UNKNOWN_PACKAGE_ID', 915 );
define( 'API_ERROR_INVALID_BILLING_DAY', 916 );
define( 'API_ERROR_SITEWORX_SAVE_FAILED', 917 );
define( 'API_ERROR_PACKAGE_SAVE_FAILED', 918 );
define( 'API_ERROR_SETTING_MASTER_DOMAIN', 919 );
define( 'API_ERROR_ACTIVATING_ACCOUNT', 920 );
define( 'API_ERROR_MAPPING_ACCOUNT', 921 );
define( 'API_ERROR_CREATING_SITEWORX_USER', 922 );
define( 'API_ERROR_EDITING_SITEWORX_USER', 923 );
define( 'API_ERROR_EDITING_SITEWORX_PACKAGE', 924 );
define( 'API_ERROR_EDITING_SITEWORX_ACCOUNT', 925 );
define( 'API_ERROR_UID_DOESNT_MATCH_USER', 926 );
define( 'API_ERROR_GID_DOESNT_MATCH_USER', 927 );
define( 'API_ERROR_UID_EXISTS', 928 );
define( 'API_ERROR_GID_EXISTS', 929 );
define( 'API_ERROR_EMPTY_LANGUAGE', 930 );
define( 'API_ERROR_EMPTY_STATUS', 940 );
define( 'API_ERROR_INVALID_PACKAGE_OPTION', 950 );
define( 'API_ERROR_UNIQNAME_EXISTS' , 960 );
define( 'API_ERROR_INVALID_UNIQNAME' , 961 );
define( 'API_ERROR_RESELLER_STORAGE_REACHED', 970 );
define( 'API_ERROR_RESELLER_ACCOUNT_REACHED', 971 );
define( 'API_ERROR_RESELLER_CHANGE_NOT_ALLOWED', 972 );
define( 'API_ERROR_RESELLER_MISSING_NAMESERVERS', 973 );
define( 'API_ERROR_DOMAIN_SUSPENDED', 1001 );
define( 'API_ERROR_DOMAIN_NOT_FOUND', 1002 );
define( 'API_ERROR_DOMAIN_UNSUSPENDED', 1101 );
define( 'API_ERROR_SITEWORX_DELETE', 1102 );
define( 'API_ERROR_PACKAGE_EXISTS', 1301 );
define( 'API_ERROR_NO_PACKAGE', 1414 );
define( 'API_ERROR_LOAD_PACKAGE', 1415 );
define( 'API_ERROR_MOUNT_ALREADY_EXISTS', 2000 );
define( 'API_ERROR_DIRECTORY_DOES_NOT_EXIST', 2001 );
define( 'API_ERROR_INVALID_REMOTE_DIRECTORY', 2002 );
define( 'API_ERROR_INVALID_HOST', 2003 );
define( 'API_ERROR_INVALID_OPTION', 2004 );
define( 'API_ERROR_MOUNT_FAILED', 2005 );
define( 'API_ERROR_UNMOUNT_FAILED', 2006 );
define( 'API_ERROR_EXPORT_FAILED', 2007 );
define( 'API_ERROR_UNEXPORT_FAILED', 2008 );
define( 'API_ERROR_INVALID_ROLE', 2020 );
define( 'API_ERROR_NODE_NOT_CLUSTERED', 2021 );
define( 'API_ERROR_INI_UPDATE_FAILED', 2030 );
define( 'API_ERROR_SQL_FILE_UPDATE_FAILED', 2031 );
define( 'API_ERROR_NO_BACKUP_DSN', 2032 );
define( 'API_ERROR_INVALID_VIP', 2033 );
define( 'API_ERROR_VIP_BIND_FAILED', 2034 );
define( 'API_ERROR_VIP_UNBIND_FAILED', 2035 );
define( 'API_ERROR_INVALID_NODEWORX_ACCOUNT', 2040 );
define( 'API_ERROR_INVALID_SITEWORX_ACCOUNT', 2041 );
define( 'API_ERROR_DNSSYNC_HOST_EXISTS', 2050 );
define( 'API_ERROR_DNSSYNC_RESOLVING_HOST', 2051 );
define( 'API_ERROR_DNSSYNC_RESOLVED_IP_DIFF', 2052 );
define( 'API_ERROR_DNSSYNC_HOST_IS_SELF', 2053 );
define( 'API_ERROR_DNSSYNC_HOST_IS_ACTIVE', 2054 );
define( 'API_ERROR_DNSSYNC_HOST_SAVE_FAILED', 2055 );
define( 'API_ERROR_DNSSYNC_HOST_ISNT_ACTIVE', 2056 );
define( 'API_ERROR_DNSSYNC_VALIDATION', 2057 );
define( 'API_ERROR_DNSSYNC_ADDITION', 2058 );
define( 'API_ERROR_DNSSYNC_INVALID_ROLE', 2059 );
define( 'API_ERROR_DNSSYNC_DELETION', 2060 );
define( 'API_ERROR_DNSSYNC_NO_SUCH_HOST', 2061 );
define( 'API_ERROR_DNSSYNC_NO_DATAFILE', 2062 );
define( 'API_ERROR_DNSSYNC_EXPORT_ERROR', 2063 );
define( 'API_ERROR_DNSSYNC_CLIENT_ERROR', 2064 );
define( 'API_LICENSED_ACCOUNT_LIMIT_REACHED', 3000 );
define( 'API_SLAVE_DOMAIN_LIMIT_REACHED', 3010 );
define( 'API_ERROR_SLAVE_DOMAIN_EXISTS', 3011 );
define( 'API_SLAVE_DOMAIN_INVALID_IP_TYPE', 3012 );
define( 'API_POINTER_DOMAIN_LIMIT_REACHED', 3020 );
define( 'API_ERROR_POINTER_DOMAIN_EXISTS', 3021 );
define( 'API_ERROR_DOMAIN_ACTIVATION_FAILED', 3030 );
define( 'API_ERROR_DOMAIN_EXISTS_ELSEWHERE', 3040 );
define( 'API_ERROR_SYNCING_SERVERALIAS', 3050 );
define( 'API_ERROR_SYNCING_VHOST', 3051 );