For a Shopify store. Nothing to install, no plugin and no script: you paste a link. First connect your shop at /integrator/connect (or with your agent: /integrator/agent-guide) and note your <slug>.
Steps
Open the product, and in the description editor switch to the HTML (source) view.
Paste markup A at the end of the description and save.
For link C, add a text block with the shop link to the footer or home page in the theme editor.
Shopify's checkout does not take third-party scripts, and this needs none: B is a plain link, put it in the cart page text.
The links
A, button at a product: https://apibase.pro/m/<slug>/p/<sku>
B, button at checkout: https://apibase.pro/m/<slug>/cart?items=<sku>:1
C, "AI purchase" block on the home page: https://apibase.pro/m/<slug>
Use the link text "Buy with your AI agent". Ready-made markup for each: /integrator#options.
Menu names change between versions of the builder; the link itself does not. Check the result at /integrator/check/<slug>.