I need to use Gmail Postmaster Tools API, but in google documentation I don't find it that useful. I am facing issue in finding out which API key to use and what credentials to create, like Service Account or OAuth 2. I want to test it locally. Here is the curl command I am using:

```
curl   'https://gmailpostmastertools.googleapis.com/v1beta1/domains/www.example.com/trafficStats/20200705?access_token=[ACCESS_TOKEN]'   --header 'Accept: application/json'   --compressed

```

Response:

```
{
  "error": {
    "code": 403,
    "message": "The caller does not have permission",
    "status": "PERMISSION_DENIED"
  }
}

```