> ## Documentation Index
> Fetch the complete documentation index at: https://docs.agentcard.sh/llms.txt
> Use this file to discover all available pages before exploring further.

# buy_set_item_quantity

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

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

**Behavior:** idempotent.

<Note>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.</Note>

## What it does

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

## Inputs

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

## Returns

None.

## Example call

```json theme={null}
{
  "tool": "buy_set_item_quantity",
  "arguments": {
    "merchant": "\u2026",
    "product_id": "\u2026",
    "quantity": "\u2026"
  }
}
```