...
name (Optional) String. Either the first, last name or both must be present.
login (Optional). String. Login name of the user. If login is present, the user will be counted towards your license count.
password (Optional). String. Password of the user.
email (Optional). String. Email of the user. For users with login, email is mandatory.
privileges (Optional). Numeric. Values of 0, 1 or 2. 0 means view tasks, 1 means view updates, 2 means add updates.
template_client_id (Numeric). ID of the client whose preferences (Input/Display date format, dashboard, privileges) to be copied.
custom_field_1 (Optional). The custom field attached to client. You need to use the Formula Key of the custom field.
When your data format is XML, you should post something like this:
...