Hello Tony,
Thanks for reaching out.
Currently, the only way to find the payload for webhooks is through webhook events only. However, we are mentioning the payload for the 
Subscription_renew webhook for your reference.
========================
{
  "event_type": "subscription_renew",
  "event_source": "scheduler",
  "data": {
    "plan": {
      "plan_active": "true",
      "payment_gateway": "all",
      "failed_payment_gateway": "",
      "failed_payment_gateway_array": [],
      "gateways_array": [],
      "createdAt": "2021-07-04T08:33:59.171Z",
      "updatedAt": "2021-07-05T07:03:31.986Z",
      "id": "60e17277e530386d9b661cb7",
      "product_id": "60e00cdd5accc45e1f29437f",
      "user_id": "60dff69f073dfa65f6a6b07d",
      "plan_name": "Weekly Plan",
      "plan_code": "weekly-plan",
      "price": 5,
      "billing_period": "w",
      "billing_period_num": "1",
      "billing_cycle": "lifetime",
      "billing_cycle_num": "",
      "trial_period": 0,
      "setup_fee": 20,
      "plan_description": "<p>This is the weekly plan.</p>"
    },
    "setup_fee": 20,
    "payment_terms": "",
    "currency_symbol": "$",
    "coupon": {
      "status": "active",
      "apply_to": "plan_amount",
      "createdAt": "2021-07-05T06:56:23.440Z",
      "updatedAt": "2021-07-05T07:05:14.561Z",
      "id": "60e2ad17dcbb4a7b23c31220",
      "user_id": "60dff69f073dfa65f6a6b07d",
      "product_id": "60e00cdd5accc45e1f29437f",
      "coupon_name": "Coupon15",
      "coupon_code": "C1",
      "discount": 1,
      "discount_type": "flat",
      "redemption_type": "onetime",
      "redemption_cycle": 0,
      "associate_plans": "selected_plans",
      "plans_array": [
        "60e17277e530386d9b661cb7"
      ],
      "valid_upto": "2021-07-31",
      "maximum_redemption": 5,
      "used_redemption": 1,
      "discount_amount": 1
    },
    "payment_method": "60e2d2d5dcbb4a7b23c315ea",
    "taxable": true,
    "gateway_type": "test",
    "gateway_id": "60e00ca65accc45e1f294372",
    "custom_fields": [],
    "cron_process": "done",
    "about_notification": {},
    "renew_count": 4,
    "createdAt": "2021-07-05T09:37:25.231Z",
    "updatedAt": "2021-08-02T10:10:02.687Z",
    "id": "60e2d2d5dcbb4a7b23c315e7",
    "customer_id": "60e2c7a3dcbb4a7b23c31498",
    "product_id": "60e00cdd5accc45e1f29437f",
    "plan_id": "60e17277e530386d9b661cb7",
    "amount": 5,
    "user_id": "60dff69f073dfa65f6a6b07d",
    "email_id": "
[email protected]",
    "status": "live",
    "quantity": 1,
    "starts_at": "2021-07-05T09:37:25.252Z",
    "activation_date": "2021-08-02T10:10:02.022Z",
    "expiry_date": "2121-07-05T09:37:25.252Z",
    "trial_days": 0,
    "trial_expiry_date": "",
    "next_billing_date": "2021-08-09T09:37:25.252Z",
    "last_billing_date": "2021-08-02T09:37:25.252Z",
    "canceled_date": null,
    "customer": {
      "billing_address": {
        "street1": "XYZ",
        "city": "XYZ",
        "state": "XYZ",
        "state_code": "XYZ",
        "zip_code": "XYZ",
        "country": "XYZ"
      },
      "shipping_address": {},
      "id": "60e2c7a3dcbb4a7b23c31498",
      "createdAt": "2021-07-05T08:49:39.447Z",
      "updatedAt": "2021-07-13T11:26:57.857Z",
      "first_name": "XYZ",
      "last_name": "XYZ",
      "email_id": "
[email protected]",
      "credit": null
    }
  },
  "create_time": "2021-08-02T10:10:03.581Z"
}
====================