WordPress at a glance
filter is not described

rest_prepare_theme filter-hook . WP 5.0.0

Filters theme data returned from the REST API.

Usage

add_filter( 'rest_prepare_theme', 'filter_function_name_5708', 10, 3 );
function filter_function_name_5708( $response, $theme, $request ){
	// filter...

	return $response;
}
$response(WP_REST_Response)
The response object.
$theme(WP_Theme)
Theme object used to create response.
$request(WP_REST_Request)
Request object.

Where the hook is called

WP_REST_Themes_Controller::prepare_item_for_response()
wp-includes/rest-api/endpoints/class-wp-rest-themes-controller.php 139
return apply_filters( 'rest_prepare_theme', $response, $theme, $request );

Where the hook is used (in WP core)

Does not used.