Server list

effectset motd to <text>since 1.5.2

The message of the day. \n starts the second line; & colour codes work · Spigot and Paper

set motd to random item of ["&6Welcome!", "&bNew: sky islands", "&dVote for rewards"]

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effectset max players to <number>since 1.5.2

The limit shown after the slash. The real limit stays as it is · Spigot and Paper

set max players to 100

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effectset shown players to <number>since 1.5.2

The online count shown · Paper

set shown players to server.online_players + 20

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effectset player list to <text>, <text>, ...since 1.5.2

The lines shown when the mouse rests on the player count; a list value works too · Paper

set player list to "&6Welcome!", "&7Survival and minigames", "&7discord.gg/example"

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effecthide player countsince 1.5.2

Shows ??? instead of the counts · Paper

on server ping:
    hide player count

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effectset server icon to <path>since 1.5.2

The icon: a 64 by 64 pixel PNG inside the plugin folder, such as "plugins/HyperScript/icon.png" · Spigot and Paper

on server ping:
    set server icon to "plugins/HyperScript/icon.png"

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Guide and examples

on server ping runs whenever a client refreshes its server list, and can change what that client sees: the message of the day, the player counts and the icon.

on server ping:
    set motd to "&6My Server &7- &a%server.online_players% online\n&eDouble coins weekend!"
    set max players to 100
    set shown players to server.online_players + 20
    set player list to "&6Welcome!", "&7Survival and minigames", "&7discord.gg/example"

Statement	Changes	Server
`set motd to <text>`	The message of the day. `\n` starts the second line; `&` colour codes work	Spigot and Paper
`set max players to <number>`	The limit shown after the slash. The real limit stays as it is	Spigot and Paper
`set shown players to <number>`	The online count shown	Paper
`set player list to <text>, <text>, ...`	The lines shown when the mouse rests on the player count; a list value works too	Paper
`hide player count`	Shows `???` instead of the counts	Paper
`set server icon to <path>`	The icon: a 64 by 64 pixel PNG inside the plugin folder, such as `"plugins/HyperScript/icon.png"`	Spigot and Paper

%server.motd% is the MOTD from server.properties, and %event.address% the IP address of the client asking. To rotate messages, pick one at random:

on server ping:
    set motd to random item of ["&6Welcome!", "&bNew: sky islands", "&dVote for rewards"]

There is no player in this event. The client has not logged in yet, so {%player%.*} variables and the player placeholders are unset. Global variables work.
It runs very often, and not on the server thread, so every refresh of every client's list triggers it. Keep the block to a few set lines: no loops, files or web requests.
A statement marked Paper does nothing on Spigot except log one warning.
Clients cache the icon and refresh the list at their own pace, so a change can take a moment to show.