What's the minimum amount of code needed to have a field show up in Manage Fields?
You have already created the definition of the field, but you also need to create an actual instance of that field to use it.

$instance = array(
    'field_name' =&gt; $your_field_name,
    'entity_type' =&gt; 'node', 
    'label' =&gt; $your_field_label, 
    'bundle' =&gt; 'node', 
  );

field_create_instance($instance);


That plus what you have above should be the minimum you need to get a field to appear in your management screen.

See the field_create_instance() docs for more info about available options.