Google Shopping Schema Reference

Exported Object: Product Reviews data
Exported Object represents: Your product reviews data.
Object is exported in these formats: CSV
Exported object has the following fields:
Data Field *	Field Definition	Data Field Type
* The preceding fields represent key data fields for the purposes of parsing and ingesting the relevant data exports. Data fields produced in an export vary by service and user action and some services or actions don't produce each data field described.
creation_time	The time the user created the comment.	timestamp
title	The title the user gave their review of the product.	string
comment	The comment that represents the user's review of the product.	string
rating	The rating the user gave the product from one to five. The closer to five, the higher the rating.	string

Exported Object: Merchant Reviews data
Exported Object represents: Your merchant reviews data.
Object is exported in these formats: CSV
Exported object has the following fields:
Data Field *	Field Definition	Data Field Type
* The preceding fields represent key data fields for the purposes of parsing and ingesting the relevant data exports. Data fields produced in an export vary by service and user action and some services or actions don't produce each data field described.
creation_time	The time the user created the comment.	time
comment	The comment. The user's review of the merchant.	string
rating	The rating the user gave the merchant from one to five. The closer to five, the higher the rating.	string

A table representing Resource Groups and the objects that are exported with it.
* Resource Group	Description	Exported Objects
shopping.reviews	This resource group contains reviews you wrote about products and online stores on Google Search, including creation date, comments, and rating.	Product Reviews data Merchant Reviews data
shopping.addresses	This resource group contains your shipping information on Shopping, including name, address, and phone number.	Addresses data
* To obtain the OAuth Scope Name for a particular Resource Group, append "https://www.googleapis.com/auth/dataportability." to the Resource Group. For example, the OAuth Scope Name for the "myactivity.search" Resource Group is "https://www.googleapis.com/auth/dataportability.myactivity.search".