# In stock subscriptions An "in-stock" subscription tracks the customer interest for an SKU that has gone out of stock in a given market. When the SKU returns back in stock, all the active subscriptions receive a 'notify' event and you can attach a webhook to actually notify the customer via email or any other channel. It's possible to set a `stock_threshold` as the minimum value to identify an SKU as back in stock (default is `1`). --- # Agent Instructions: Querying This Documentation If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question. Perform an HTTP GET request on the current page URL with the `ask` query parameter: ``` GET https://docs.commercelayer.io/core-api-reference/in_stock_subscriptions.md?ask= ``` The question should be specific, self-contained, and written in natural language. The response will contain a direct answer to the question and relevant excerpts and sources from the documentation. Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.