Need field properties

I want to add field to my form programatically.

Can you provide the whole list of all properties I need to set?

I set these but I'm getting error. What else I have to set here?

$form['my_url'] = array(
					'#type' => 'link_field',
					'#title' => t('My link'),
					'#default_value' => array('url' => 'http://'),
					'#maxlength' => 255,
					'#size' => 60,				
					'#description' => t('Please enter your URL'),
					'#weight' => 10,
				);