In CRM 2013, Microsoft has introduced the concept of actions which is a wonderful way to represent you custom business functionality in the form of a request that CRM platform would understand. Also on top of that, you can register plugins for the actions you create. However there are certain limitations when using plugins with actions.
To illustrate this, lets start with a simple example.
Say we create an action for contact entity named “new_TestAction” as shown in the screenshot below.
Now we open the plugin registration tool and try to register a plugin on post execution of the action. As you can see from the below screenshot, filtering attributes are not supported in that case.
Also let us try to register a post image on the plugin. As you can see from the below screenshot, CRM would not allow you to register that image and gives u an error.
So if you have a requirement to register a plugin on post execution of an action, please keep these limitations in minds and design accordingly.
Hope this helps!