You can Update Product Stock related information by REST API with the use of endpoint URL /V1/products/:productSku/stockItems/:itemId.
You can manage Stock Inventory related data with REST API with the given payload as below.
Action: PUT
Header: Authorization: Bearer <ADMIN_TOKEN>
URL: <BASE_URL>/V1/products/:productSku/stockItems/:itemId
(Example, https:/magento246.test/rest/V1/products/24-MB01/stockItems/90)
You can fetch itemId by calling the GET Product StockItems API. Product Stock Item by REST API V1/stockItems/:SKU Magento 2?
PAYLOAD:
{ "stockItem": { "product_id": 12, "stock_id": 1, "qty": 1030, "is_in_stock": true, "is_qty_decimal": true, "use_config_min_qty": true, "min_qty": 0, "use_config_min_sale_qty": 0, "min_sale_qty": 0, "use_config_max_sale_qty": true, "max_sale_qty": 0, "use_config_backorders": true, "backorders": 0, "use_config_notify_stock_qty": true, "notify_stock_qty": 0, "use_config_qty_increments": true, "qty_increments": 0, "use_config_enable_qty_inc": true, "enable_qty_increments": true, "use_config_manage_stock": true, "manage_stock": true, "low_stock_date": "", "is_decimal_divided": true, "stock_status_changed_auto": 0, "extension_attributes": {} } }
All the fields are self-explanatory. You can set qty, is_in_stock to set your product In stock and Qty value.
RESPONSE: Item Id.