Installation failure on no plugin-description.properties

[pscheidlerSr]

On installation from a file I received the message below. Looking at the zip, the properties file was indeed absent. On the other hand, there might be something I don't understand going on since my experience with ES is limited.

c:\LoS\elasticsearch-2.2.0\bin>plugin install file:/C:/LoS/downloads/elastic-hammer-master.zip
-> Installing from file:/C:/LoS/downloads/elastic-hammer-master.zip...
Trying file:/C:/LoS/downloads/elastic-hammer-master.zip ...
Downloading ....DONE
Verifying file:/C:/LoS/downloads/elastic-hammer-master.zip checksums if available ...
NOTE: Unable to verify checksum for downloaded plugin (unable to find .sha1 or .md5 file to verify)
ERROR: Could not find plugin descriptor 'plugin-descriptor.properties' in plugin zip

[apiszcz]

Is there a resolution for this, I'm seeing the same error.