Under the Tools>Add-ins menu, there is a box for a description. To add a description to your .xla add-in, modify the file properties. First, locate the file in Windows Explorer, right-click on it and select properties.
In the Properties dialog, select the Summary tab. If you don’t see a Summary tab, it may be that the file is in use. Close Excel, and thus the add-in, and repeat this step.
Put your description in the Comments box and click OK. Now, the description will display in Excel.
You can also add comments to an Addin on the worksheet under File > Properties, Summary Tab Comments.