Which hook is used to alter a field's description? Which hook should I use to alter description of a field?

I want to add some descriptions to fields in several content types. because number of fields and content types are too many, I prefer to add descriptions programmatically.
To the best of my knowledge there's no hook for that. Instead you'll want to use the following API functions in whatever context makes sense in your site:


field_info_instance()


  Returns an array of instance data for a specific field and bundle.


Use the function to load up an array of instance data/settings, which you can then alter as necessary before passing back to:
field_instance_update()


  Updates an instance of a field.


That will persist your changes to the database, and take care of clearing relevant caches.


A complete example might look like

$info = field_info_instance('node', 'body', 'article');
$info['description'] = t('New description');
field_instance_update($info);