JSON for a query value widget that will count the number of agents reporting and also provide coloring options.

queryvalue_how_many_agents

{
  "viz": "query_value",
  "requests": [
    {
      "q": "count_not_null(avg:system.cpu.system{*} by {host})",
      "conditional_formats": [
        {
          "comparator": "<=",
          "value": "1",
          "palette": "white_on_red"
        },
        {
          "comparator": "<=",
          "value": "2",
          "palette": "white_on_yellow"
        },
        {
          "comparator": ">",
          "value": "2",
          "palette": "white_on_green"
        }
      ],
      "aggregator": "last"
    }
  ],
  "precision": "0"
}