buy_set_item_quantity

Connect to https://mcp.agentcard.sh/mcp with the user’s connection token (or a buy_token for org-owned accounts). Behavior: idempotent.

Not in the default tools/list. It is still callable by exact name, and appears when the client sends the x-expert-tools: 1 header.

What it does

Set a product’s quantity in the cart (0 removes it).

Field	Type	Description
`merchant` (required)	string
`product_id` (required)	string
`quantity` (required)	number	new quantity; 0 removes the item

None.

{
  "tool": "buy_set_item_quantity",
  "arguments": {
    "merchant": "\u2026",
    "product_id": "\u2026",
    "quantity": "\u2026"
  }
}