Custom module hook entity presave not 'firing' I've seen other posts and did all the good things, I think... still not firing.

I use Commerce Kickstart 2 in Drupal 7

I want my module to be called for the hook_entity_presave event.

I followed the docs to create my custom module: call it 'Update Description'
I put my new mod in sites/all/modules/update_description

update_description.info
update_description.module


I named the files and added the appropriate info

name = Update Description
description = This module populates a description field based on the selected product attributes. 
core = 7.x


I see, and enabled the module in the modules list, and I cleared cache

The module looks for a type of entity, and updates it:

function update_description_hook_entity_presave($entity, $type){
    $entity-&gt;changed = REQUEST_TIME;
    $vari_result = "";

    watchdog('update_description', 'type: ' . $entity-&gt;type, array(), WATCHDOG_DEBUG, NULL);

    if($entity-&gt;type == 'my_new_content_type' &amp;&amp; $entity-&gt;product_id &amp;&amp; $entity-&gt;revision_id) {
        // do stuff
        /// watchdog the results
    }
}


But I never see any log messages show up when I create or update an item of 'my_new_content_type', other than the default creation 'info' log message that happens anyway.

What do I need to do to get this my module to 'hook' into this call?
The hook_ part is for example only; it should be replaced completely by your module's name:

function update_description_entity_presave($entity, $type) {