Let’s say I have a job ID for a server within another game that I cannot manage. Are there endpoints that can give me information such as the amount of players on that server?
To avoid misunderstanding, there are 3 types of IDs within a game. There is the game ID/universe ID which represents the entire universe/collection of places, the place ID which represents a specific place within an experience, and the job ID which represents a specific server within a place.
You can look up in messging service Roblox Documents
MessagingService:SubscribeAsync("Password", function(message)
print("Received message: ", message)
end)
MessagingService:PublishAsync("Password", "Hello i sent this message by server script")
^^^
That’s why I mention API endpoints, I don’t have access to the experiences to be able to run code in them. Therefore all solutions related to communication between servers or datastores simply don’t work.
You can use this endpoint “https://games.roblox.com/v1/games/ID/servers/0?sortOrder=2&excludeFullGames=false&limit=10” to get all running servers on a game then just loop through it to find the id
Is there a more direct method?
Why you need something like this? 
No not really I think roblox tried to make it hard as it could of been a way the auto join bots worked