Change plugin descriptions

Yes, there is a filter you can use — all_plugins:

apply_filters( 'all_plugins', array $all_plugins )

Filters the full array of plugins to list in the Plugins list table.

And here’s an example which changes the description of the Akismet plugin:

add_filter( 'all_plugins', 'my_all_plugins' );
function my_all_plugins( $all_plugins ) {
    // the & means we're modifying the original $all_plugins array
    foreach ( $all_plugins as $plugin_file => &$plugin_data ) {
        if ( 'Akismet Anti-Spam' === $plugin_data['Name'] ) {
            $plugin_data['Description'] = 'My awesome description';
        }
    }

    return $all_plugins;
}

But yes, the above hook runs on the Plugins list table only..

^{*my_all_plugins is just an example name. You should use a better one..}