Structured data
Structured data is information on your web page written in a standard, machine-readable format (usually schema.org markup in JSON-LD) that tells an AI agent or search engine exactly what something is: this is a product, this is its price, this is its availability. Without it, a machine has to guess from the text.
How it works
Structured data sits in your page's HTML, most often as a block of schema.org markup in a format called JSON-LD. It labels the parts of your page so a machine does not have to infer them: it states that a number is the price, that a string is the brand, that the item is in stock. AI crawlers read the HTML your server sends and mostly do not run JavaScript, so this markup needs to be in the page that arrives, not added later in the browser.
A commerce example
Your product page shows "$148" in a styled graphic and the availability as a green dot. A person understands both instantly. An agent reading the raw HTML may see neither. Put the price and availability in Product and Offer structured data and the agent can state them with confidence, which is often the difference between being compared and being skipped.
What this means for your store
On Shopify and WooCommerce the basics are usually present, but brand and barcode-level identifiers often are not unless a plugin adds them. A mainstream SEO plugin can extend your product markup, and you can confirm it with Google's Rich Results Test. This is one of the highest-payoff, lowest-effort parts of agentic commerce optimization.