WordPress at a glance
filter is not described

themes_api filter-hook . WP 2.8.0

Filters whether to override the WordPress.org Themes API.

Passing a non-false value will effectively short-circuit the WordPress.org API request.

If $action is 'query_themes', 'theme_information', or 'feature_list', an object MUST be passed. If $action is 'hot_tags', an array should be passed.

Usage

add_filter( 'themes_api', 'filter_function_name_8408', 10, 3 );
function filter_function_name_8408( $override, $action, $args ){
	// filter...

	return $override;
}
$override(false/object/array)
Whether to override the WordPress.org Themes API.
Default: false
$action(string)
Requested action. Likely values are 'theme_information', 'feature_list', or 'query_themes'.
$args(object)
Arguments used to query for installer pages from the Themes API.

Where the hook is called

themes_api()
wp-admin/includes/theme.php 441
$res = apply_filters( 'themes_api', false, $action, $args );

Where the hook is used (in WP core)

Does not used.