ha-core/homeassistant/components/snapcast/services.yaml

join:
  description: Group players together.
  fields:
    master:
      description: Entity ID of the player to synchronize to.
      example: "media_player.living_room"
    entity_id:
      description: Entity ID of the players to join to the "master".
      example: "media_player.bedroom"

unjoin:
  description: Unjoin the player from a group.
  fields:
    entity_id:
      description: Entity ID of the player to unjoin.
      example: "media_player.living_room"

snapshot:
  description: Take a snapshot of the media player.
  fields:
    entity_id:
      description: Name(s) of entities that will be snapshotted. Platform dependent.
      example: "media_player.living_room"

restore:
  description: Restore a snapshot of the media player.
  fields:
    entity_id:
      description: Name(s) of entities that will be restored. Platform dependent.
      example: "media_player.living_room"

set_latency:
  description: Set client set_latency
  fields:
    entity_id:
      description: Name of entities that will have adjusted latency
    latency:
      description: Latency in master
      example: 14