It will give you all the matches it knows about. There’s no single authoritative source for Crystal shards, though, because they’re completely decentralized. That makes it impossible to index every shard in existence. You can only index what you can find.
Yes, i consider the issue is, the most well known jwt shards (which used by lucky, and list on jwt offical site JSON Web Token Libraries - jwt.io could not find on https://crystalshards.org, that should be consider as a issue anyway.