minecraft-packets/minecraft-packets/data/pc/1.12.2/from-server/chat/1.json

An easy way to query PrismarineJS/minecraft-packets

{
  "message": "{\"italic\":true,\"color\":\"gray\",\"translate\":\"chat.type.admin\",\"with\":[\"Server\",{\"translate\":\"commands.op.success\",\"with\":[\"nmptestbot\"]}]}",
  "position": 1
}