PayPal支付API错误

我在https://developer.paypal.com/docs/integration/direct/create-single-payout/但不断得到这个错误：

数组（[名称]=>MALFORMED_REQUEST_ERROR[消息]=>Json请求格式错误。[调试id]=>aef61e278b531[信息链接]=>https://developer.paypal.com/webapps/developer/docs/api/#MALFORMED_REQUEST_ERROR）

这是卷曲请求：

curl -v https://api.sandbox.paypal.com/v1/payments/payouts?sync_mode=true '
-H "Content-Type: application/json" '
-H "Authorization: Bearer <Access-Token>" '
-d "{
"sender_batch_header": {
        "email_subject": "You have a payment"
    },
    "items": [
        {
            "recipient_type": "EMAIL",
            "amount": {
                "value": 12.34,
                "currency": "USD"
            },
            "receiver": "shirt-supplier-one@mail.com",
            "note": "Payment for recent T-Shirt delivery",
            "sender_item_id": "A123"
        }
    ]
}"

错误文档说JSON格式错误，但后来我使用jsonint来确保它是一个有效的JSON。它可能是什么？