Amazon Offer Listing API: Every Seller, Price and Condition for an ASIN

To get every offer on an Amazon listing, call the SellerMagnet /api/amazon-product-offers endpoint with the ASIN and marketplace. The response lists each offer with its seller, condition, FBA or FBM fulfilment, item price, shipping, landed price, delivery date and seller rating, and names the featured offer separately as buyBox. One request costs one credit and reads the offer listing live, so the prices are the ones a shopper sees right now.

What does the offer listing API return?

The endpoint reads one page of Amazon's offer listing - the panel behind Other sellers on Amazon: the featured offer plus the offers Amazon loads first. There is no paging parameter. Each offer appears once: rows from the same seller with the same condition, fulfilment and delivery date are kept once - the first row wins. Prices are decimal numbers in the marketplace currency; offers[].totalPrice is rounded to two places, so round the buyBox copy yourself before comparing.

Response from /api/amazon-product-offers on amazon.com (trimmed, sellers anonymised)

{
  "success": true,
  "data": {
    "asin": "B0CL61F39H",
    "marketplaceId": "ATVPDKIKX0DER",
    "currency": {"symbol": "$", "code": "USD", "name": "United States Dollar"},
    "buyBoxSuppressed": false,
    "buyBox": {
      "sellerId": "Amazon", "amazonSellerId": "ATVPDKIKX0DER", "sellerName": "Amazon",
      "condition": "New", "fulfillmentType": "FBA",
      "priceWithoutShipping": 499.0, "shippingPrice": 0.0, "totalPrice": 499.0,
      "deliveryDate": "2025-06-28", "inventory": 30, "totalReviews": 0, "positivePercentage": 0
    },
    "offers": [
      {"sellerId": "Amazon", "amazonSellerId": "ATVPDKIKX0DER", "sellerName": "Amazon", "condition": "New",
       "fulfillmentType": "FBA", "priceWithoutShipping": 499.0, "shippingPrice": 0.0, "totalPrice": 499.0,
       "deliveryDate": "2025-06-28", "inventory": 30, "totalReviews": 0, "positivePercentage": 0},
      {"sellerId": "A17J18A7XABQI9", "amazonSellerId": null, "sellerName": "Example Seller",
       "condition": "Used - Very Good", "fulfillmentType": "FBM", "priceWithoutShipping": 409.99,
       "shippingPrice": 0.0, "totalPrice": 409.99, "deliveryDate": "2025-07-07", "inventory": 10,
       "totalReviews": 6892, "positivePercentage": 78}
    ]
  }
}

How do I compare Amazon offers fairly?

Compare landed prices of offers in the same condition. An FBM offer at 409.99 plus 12.00 shipping costs the shopper more than an FBA offer at 419.83 with free shipping, and a used console is not a competitor for a new one. The Buy Box is not simply the lowest price either: Amazon weighs fulfilment, delivery speed and seller rating, so a cheaper offer can sit behind the featured one.

offer_summary.py - the competition on one listing, one credit

import os
from collections import Counter

import requests


def offers(asin: str, marketplace_id: str) -> dict:
    resp = requests.get("https://sellermagnet-api.com/api/amazon-product-offers",
                        params={"asin": asin, "marketplaceId": marketplace_id},
                        headers={"X-Api-Key": os.environ["SELLERMAGNET_API_KEY"]}, timeout=120)
    try:
        body = resp.json()
    except ValueError:  # e.g. an HTML error page from a proxy
        body = {}
    if resp.status_code != 200 or not body.get("success"):
        raise RuntimeError(f"{asin}: {resp.status_code} {body.get('message')}")
    return body["data"]


def summarise(data: dict, my_seller_id: str | None = None) -> dict:
    new = [o for o in data["offers"] if o["condition"] == "New" and o["totalPrice"] > 0]
    by_channel = Counter(o["fulfillmentType"] for o in new)
    floor = {ch: min((o["totalPrice"] for o in new if o["fulfillmentType"] == ch), default=None)
             for ch in ("FBA", "FBM")}
    box = data.get("buyBox") or {}
    mine = next((o for o in new if o["sellerId"] == my_seller_id), None)
    return {
        "new_offers": len(new),
        "fba_sellers": by_channel["FBA"], "fbm_sellers": by_channel["FBM"],
        "lowest_new_fba": floor["FBA"], "lowest_new_fbm": floor["FBM"],
        "buy_box": None if not box else (box["sellerName"], box["totalPrice"]),
        "amazon_on_listing": any(o["sellerName"] == "Amazon" for o in new),
        "my_gap_to_buy_box": round(mine["totalPrice"] - box["totalPrice"], 2) if mine and box else None,
    }


print(summarise(offers("B0CL61F39H", "ATVPDKIKX0DER")))

What does the inventory field mean?

inventory is the maximum quantity Amazon lets a shopper add to the cart for that offer, read from the offer's add-to-cart button. For large sellers it is usually a per-order limit such as 10 or 30; for a seller with two units left it can be 2. Treat it as a lower bound on stock at best, never as a stock count - a value of 30 says nothing about whether the seller has 30 or 3,000 units.

How do I list the sellers on an ASIN from the command line?

New offers sorted by landed price, with curl and jq

curl -sG "https://sellermagnet-api.com/api/amazon-product-offers" \
  -H "X-Api-Key: $SELLERMAGNET_API_KEY" \
  --data-urlencode "asin=B0CL61F39H" \
  --data-urlencode "marketplaceId=ATVPDKIKX0DER" \
  | jq -r '(.data.offers // []) | map(select(.condition == "New")) | sort_by(.totalPrice)[]
           | [.totalPrice, .fulfillmentType, .sellerName, .deliveryDate] | @tsv'

The offer listing is a snapshot. To watch who takes the featured offer over the day, the Buy Box polling guide sets the interval and cost; for how prices moved over months, the price history endpoint returns the recorded series. The endpoint does not validate the ASIN format, so a typo is sent and billed - check it locally first, as the error-handling guide explains.

Bottom line: one call returns the listing's competition, compare landed prices within one condition, and read inventory as a cart limit. The product offers page shows the endpoint, and a free account includes 150 credits.