Oracle Cloud: How to fill json file for custom metrics

I am trying to send custom t2 telemetry metrics to Oracle Cloud. Using below Command I am able to generate param json file.

oci monitoring metric-data post --generate-param-json-input metric-data > metric-data.json

Below is the generate metric-data.json file

[
  {
    "compartmentId": "string",
    "datapoints": [
      {
        "count": 0,
        "timestamp": "2017-01-01T00:00:00+00:00",
        "value": 0.0
      },
      {
        "count": 0,
        "timestamp": "2017-01-01T00:00:00+00:00",
        "value": 0.0
      }
    ],
    "dimensions": {
      "string1": "string",
      "string2": "string"
    },
    "metadata": {
      "string1": "string",
      "string2": "string"
    },
    "name": "string",
    "namespace": "string",
    "resourceGroup": "string"
  },
  {
    "compartmentId": "string",
    "datapoints": [
      {
        "count": 0,
        "timestamp": "2017-01-01T00:00:00+00:00",
        "value": 0.0
      },
      {
        "count": 0,
        "timestamp": "2017-01-01T00:00:00+00:00",
        "value": 0.0
      }
    ],
    "dimensions": {
      "string1": "string",
      "string2": "string"
    },
    "metadata": {
      "string1": "string",
      "string2": "string"
    },
    "name": "string",
    "namespace": "string",
    "resourceGroup": "string"
  }
]

My metrics requirement is below. Need to send below information in case any agent id is late or missing.

MetricsName: [late/missing]
Hostname: somexyz.oraclecloud.com
agentid: asdfkjgsjdg723
category: custom/DB/Webserver
Region: 
AD:
Information1:
Information2:

So my question is below.

1. How to accomodate my information in metric-data.json file
2. On Cloud how to visualise my data
3. Do I need to register my service on cloud before sending it