There is a built-in deployment package in Lansweeper to change the local computer description, but there isn't one for the Active Directory description. You can create your own deployment package in the Deployment tab or your own asset action in the Configuration\Asset Pages section of the web console.
General info on creating and running deployment packages can be found in
this section of our knowledge base. A customer also posted a sample asset action for changing AD computer descriptions a while ago,
here. Available action parameters are listed when you hit the Add Asset Action button under Configuration\Asset Pages. Creating specific actions or deployment packages is unfortunately not something we can provide instructions or support for.