"ASIN lookup" covers three different jobs: finding a product's ASIN, turning another identifier into an ASIN, and getting product data once you have one.
Which one you are doing depends on what you are holding. The identifier you start with decides the route, and for one of them there is no route.
Start from what you have
| You have | What to do | Works? |
|---|---|---|
| An ASIN | Query product data directly | Yes |
| A product page URL | Read the ASIN from the URL, then query | Yes |
| A UPC or EAN barcode | Search the barcode on Amazon, read the ASIN from the result, then query | Yes, in two steps |
| A product name or keyword | Search, pick the product, take its ASIN | Yes |
| Your own SKU | Look it up in your seller account | Yes, in your account only |
| A competitor's SKU | Nothing | No |
The last row surprises people. A SKU is a label a seller invents for their own stock. It is private to their account, so there is no public "SKU lookup" for someone else's product. What you can look up is the ASIN, which is public. What an ASIN is explains who assigns each identifier.
Finding the ASIN
On any product page the ASIN is the ten-character segment after /dp/:
https://www.amazon.com/dp/B08CK5Z5Q1
^^^^^^^^^^It is also listed in the product information section of the page. An ASIN is always ten characters, uppercase letters and digits.
Looking up one ASIN
The product details endpoint takes one ASIN and returns the listing as a single JSON object:
curl --request POST \
--url https://ecommercedataapi.com/v1/amazon/asin/detail \
--header "Content-Type: application/json" \
--header "X-API-Key: ${ECOMMERCE_DATA_API_KEY}" \
--data '{
"marketplace": "US",
"asin": "B08CK5Z5Q1"
}'| Field | What it tells you |
|---|---|
title, brand, parent | Which product it is and its parent listing |
price, coupon | Current price and coupon text |
bsrRank, bsrLabel, subcategories | Best Sellers Rank, its category and subcategory ranks |
rating, ratings | Star rating and rating count |
sellerName, sellers, fulfillment | Who sells it, how many sellers, how it ships |
variations, variationList | The variation family and each variation's ASIN |
features, dimensions, weight | Bullet points and physical size |
The endpoint takes an ASIN only. There is no UPC, EAN or GTIN parameter, so a barcode has to become an ASIN before you call it. The Amazon Product Data API page has the full field list.
Looking up many ASINs
Calling the detail endpoint once per product works, and for a comparison table it is the slow way. The product search endpoint accepts an asins array and returns the same comparison fields for all of them in one request:
curl --request POST \
--url https://ecommercedataapi.com/v1/amazon/product/competitor-lookup \
--header "Content-Type: application/json" \
--header "X-API-Key: ${ECOMMERCE_DATA_API_KEY}" \
--data '{
"marketplace": "US",
"asins": ["B08CK5Z5Q1", "B07Z82895W"]
}'Each item carries price, bsr, units and revenue (estimated monthly sales), rating, ratings and seller data. Send either asins or keyword, not both.
Use detail when you need the listing itself — title, bullet points, variations, attributes. Use search when you need a table to compare products on price, rank and estimated sales.
Four things that go wrong
1. The wrong marketplace. An ASIN usually exists in several marketplaces, but price, rank and reviews are separate in each. A US lookup tells you nothing about Japan.
2. Missing values. A field that does not exist for a product comes back as null or -1, for example primePrice: -1. Check before doing arithmetic.
3. Parent against child. A parent ASIN's figures cover the whole variation family; a child's cover one variation. Comparing one product's parent with another's child can be off several times over. Parent and child ASINs covers which numbers are pooled.
4. An ASIN that stops resolving. Listings get merged, split and removed. A long-running job should handle "not found" instead of assuming an ASIN is permanent.
Questions
Can I look up a product by UPC? Not in one call here. Search the UPC on Amazon, read the ASIN from the result, then look up the ASIN.
Is there an Amazon SKU lookup? For your own SKUs, in your seller account. For anyone else's, no: SKUs are private. Look up the ASIN instead.
Do I need one call per product?
For full listing data, yes. For price, rank, estimated sales and ratings, pass a list in asins and get them in one call.
Can I look up an ASIN from an AI assistant? Yes. Both endpoints are tools on the remote MCP server, so you can ask in plain language. Querying Amazon data in Claude Code shows the setup.