How to Add Custom Shipping Carrier in Fulfill Item Screen?

[AkashVerma]

Hello Shopify Community,

I need assistance adding a custom shipping carrier to the "Fulfill Items" screen (screenshot attached). I tried using the following API call:

await axios.post(
    `https://${shop}/admin/api/${LATEST_API_VERSION}/carrier_services.json`,
    {
        carrier_service: {
            name: 'Your Shipping Service',
            callback_url: `https://${process.env.HOST}/carrier-service`,
            service_discovery: true,
        },
    },
    {
        headers: {
            'X-Shopify-Access-Token': accessToken,
        },
    }
);

The API call is successful, and the carrier is created, but it doesn’t appear in the "Shipping Carrier" dropdown.

How can I ensure the carrier appears in the fulfillment screen? Any guidance or suggestions would be appreciated.

Thank you!