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Update: Item Search API spec-format and ASIN

Date: May 07, 2026

The Item Search API now supports an optional spec-format response for US integrations. This update adds a new responseFormat option and enables ASIN as a supported identifier when requesting spec-formatted results. Default behavior remains unchanged when spec-format is not used.

What changed

  • Added: responseFormat query parameter (Allowed values SPEC, DEFAULT; uppercase only). Omitted defaults to DEFAULT.

  • Added (US only): ASIN query parameter, supported only with responseFormat=SPEC.

  • Updated: Default identifier lookup UPC or GTIN) returns 0 or 1 match.

  • Updated (US only): Spec-format requests require responseFormat=SPEC and exactly one identifier UPC, GTIN, or ASIN); query is not supported.

  • Updated (US only): Spec-format outcomes:

    • Item is found and live in Walmart catalog → returns MP_ITEM_MATCH (offer setup by match)
    • Item found but not live → returns MP_ITEM (full item setup spec with available Walmart catalog attributes)
    • No match → 200 {} (items may be omitted)

Why it matters

  • Faster setup workflows: Spec-format responses provide structured content that can reduce manual mapping when preparing item setup data.
  • More identifier flexibility (US): ASIN support helps sellers match items when UPC/GTIN aren’t readily available.
  • Predictable integration behavior: Clear validation rules and deterministic outcomes reduce ambiguity and improve error handling.

Next steps

  • No action needed to keep using default behavior (omit responseFormat or use DEFAULT).
  • To use spec-format in US: send responseFormat=SPEC and exactly one identifier (UPC, GTIN, or ASIN), and handle MP_ITEM_MATCH / MP_ITEM / empty `` responses.
  • Refer to the updated Item Search documentation for request/response examples and validation rules.