Robin's tool does provide the necessary information about the messages that exist only on the local Wiki. For somebody who knows Assamese, the first step is a matter of copying the existing messages to translatewiki and verifying if they are correct. This improves support for the Assamese language on every Wiki.
|Messages not localised at translatewiki.net|
Running Robin's tool is a task that should be run on any MediaWiki wiki. When this task has been performed on many wikis, there will be enough data to indicate the messages that typically have a local override. This could be the next step in optimising your local MediaWiki setup.