Can I obtain subscribers by only going to the URL?

API
3

I recommend using headers, but yes you can use the “oauth_token” key to use a token just like the client ID.

v3

/kraken/channels/:channel login/subscriptions
?api_version=3&client_id=:client ID&oauth_token=:OAuth token

v5

/kraken/channels/:channel ID/subscriptions
?api_version=5&client_id=:client ID&oauth_token=:OAuth token

I haven’t tested much of the new API, it may or may not be available there. Again, best to the learn to use headers.