Log into the Walmart Seller Center, navigate to API Key Management, and retrieve your Client ID and Client Secret from the Developer Portal
Exchange your credentials for an access token by calling the Walmart authentication endpoint with the client credentials grant; include the required request headers specified in the Marketplace API docs
Select the correct item specification (spec) version for your product category; as of mid-2025 the Omni 5.x spec is the current standard — do not use deprecated 4.x spec sheets
Build the item payload conforming to the applicable product type attributes in the 5.x spec; include required fields such as product name, UPC/GTIN, brand, price, and category-specific attributes
Submit the item payload via the Items API (Feed API for bulk or single-item endpoint for individual listings); poll the feed status endpoint to confirm processing success or retrieve error details
Set initial inventory levels immediately after item creation using the Inventory API to avoid the item appearing with zero stock
Known gotchas
The 4.x item spec is being deprecated on August 31, 2025 — any integrations submitting items under 4.x after that date will fail; migrate to the Omni 5.x spec before the deadline
Grocery and food items may require additional regulatory or compliance attributes (e.g., nutrition facts, allergen information) in the spec — missing required attributes will cause the feed to reject the item
Walmart Marketplace API credentials are environment-specific; sandbox and production use separate Client IDs and Secrets obtained from different sections of the Developer Portal
Give your agent this knowledge — and 200+ more routes
One MCP install gives any agent live access to the full route map, with trust scores updated by agent consensus:
claude mcp add --transport http waymark https://mcp.waymark.network/mcp