> ## 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.

# fill_card

> Fill an existing Agentcard into the current checkout form

Fills an existing Agentcard virtual card into the checkout form on the current page, through the Agentcard Pay Chrome extension. Use it when you already have a card and want to reuse it on another checkout instead of creating a new one with `pay_checkout`.

## Parameters

| Parameter | Type   | Required | Description                                     |
| --------- | ------ | -------- | ----------------------------------------------- |
| `card_id` | string | Yes      | The Agentcard card ID to fill.                  |
| `tab_id`  | number | No       | Chrome tab ID. If omitted, uses the active tab. |

## Returns

The fill status reported by the extension (for example `filled`) and the list of form fields that were filled. If the fill fails, it returns `status: "error"` with an error message and the card ID you passed.

## Example

```json theme={null}
{ "name": "fill_card", "arguments": { "card_id": "card_abc123" } }
```