Amazon Reviews Summary API: Average Rating and Count from One Lookup

To get an Amazon product's review summary via API, call /api/amazon-product-lookup with the ASIN and marketplace: productInfo.reviews carries averageRating, totalReviews and Amazon's own reviewSummary text, for the same one credit a lookup already costs. A missing rating is null, not zero, so check totalReviews before trusting a star figure.

Where does the review data live in the lookup response?

How do I read the average rating and review count?

The function below returns a flat dict and a has_reviews flag so a caller never has to check totalReviews == 0 twice. It treats a missing reviews key the same as an empty one, which matters for older or thinly-stocked listings. get() and new_session() come from the Python quickstart.

reviews_summary.py - rating, count and summary from one call

from sellermagnet import ApiError, get, new_session


def reviews_summary(session, asin: str, marketplace_id: str) -> dict:
    """One /amazon-product-lookup call to the review snapshot: average rating,
    lifetime review count and Amazon's own short summary text. averageRating
    is null and totalReviews is 0 when the product has no reviews or the
    parser failed - never read that as a 0.0-star product."""
    p = get(session, "amazon-product-lookup", asin=asin, marketplaceId=marketplace_id)["productInfo"]
    reviews = p.get("reviews") or {}
    return {
        "asin": p["asin"],
        "title": p["title"],
        "average_rating": reviews.get("averageRating"),      # float or None
        "total_reviews": reviews.get("totalReviews", 0),     # int, 0 on failure
        "summary": reviews.get("reviewSummary") or None,
        "has_reviews": bool(reviews.get("totalReviews")),
    }


if __name__ == "__main__":
    session = new_session()
    for asin in ["B0CL61F39H", "B0ZEROSTARS", "B0MISSINGKEY", "B0DEADASIN"]:
        try:
            print(reviews_summary(session, asin, "ATVPDKIKX0DER"))
        except ApiError as exc:
            print(asin, "failed:", exc)

Example output (illustrative ASINs)

reviews_summary: 4 scenarios OK, calls={'amazon-product-lookup': 4}
{'asin': 'B0CL61F39H', 'title': 'Widget', 'average_rating': 4.6, 'total_reviews': 3129, 'summary': 'Customers like the build quality.', 'has_reviews': True}
{'asin': 'B0ZEROSTARS', 'title': 'Widget', 'average_rating': None, 'total_reviews': 0, 'summary': None, 'has_reviews': False}
{'asin': 'B0MISSINGKEY', 'title': 'Widget', 'average_rating': None, 'total_reviews': 0, 'summary': None, 'has_reviews': False}
B0DEADASIN failed: 404: Product not found

Trimmed reviews object (example values)

{
  "productInfo": {
    "reviews": {
      "averageRating": 4.6,
      "totalReviews": 3129,
      "reviewSummary": "Customers like the build quality."
    }
  }
}

Why does a product show no rating at all?

Either it genuinely has zero reviews (new listings, low-volume variations) or the parser found no review block on the page at that moment, both return the same null/0 shape, so a single snapshot cannot distinguish them. A second lookup a day later that still returns null/0 is stronger evidence of a real zero-review product than relying on one call. For a trend instead of a snapshot, the rating and review count history guide covers productRatingHistory, and the product lookup page lists every other field in the same response.

Bottom line: read reviews straight off a lookup you already pay for, and treat null/0 as "no reviews yet", not "zero stars".