If you are working with an extensible SDK that gets occasionally updated (e.g. typically when that SDK has been provided to you by another party), then you will need to manually pull down those updates to your installed SDK.
To update your installed SDK, run the following:
$ devtool sdk-update
The previous command assumes your SDK provider has set the default update URL for you. If that URL has not been set, you need to specify it yourself as follows:
$ devtool sdk-update path_to_update_directory