Question regarding "Store credit primitive and API developer preview"

I was testing the new Store credit primitive and API developer preview released recently and available here , for that I have Created a store to test and build from partner dashboard and create custom app in shopify admin to get the access token, with that token I have send the below GraphQL mutation to create Store credit primitive:

{"variables": {"creditInput": {"creditAmount": {"amount": "49.99", "currencyCode": "USD"}}, "id": "gid://shopify/Customer/7246127562990"}, "query": "mutation storeCreditAccountCredit($id: ID!, $creditInput: StoreCreditAccountCreditInput!) {\r\n  storeCreditAccountCredit(id: $id, creditInput: $creditInput) {\r\n    storeCreditAccountTransaction {\r\n      amount {\r\n        amount\r\n        currencyCode\r\n      }\r\n      account {\r\n        id\r\n        balance {\r\n          amount\r\n          currencyCode\r\n        }\r\n      }\r\n    }\r\n    userErrors {\r\n      message\r\n      field\r\n    }\r\n  }\r\n}\r\n"}

But I am getting an error

{
	"errors": [
		{
			"message": "StoreCreditAccountCreditInput isn't a defined input type (on $creditInput)",
			"locations": [
				{
					"line": 1,
					"column": 45
				}
			],
			"path": [
				"mutation storeCreditAccountCredit"
			],
			"extensions": {
				"code": "variableRequiresValidType",
				"typeName": "StoreCreditAccountCreditInput",
				"variableName": "creditInput"
			}
		},
		{
			"message": "Field 'storeCreditAccountCredit' doesn't exist on type 'Mutation'",
			"locations": [
				{
					"line": 2,
					"column": 3
				}
			],
			"path": [
				"mutation storeCreditAccountCredit",
				"storeCreditAccountCredit"
			],
			"extensions": {
				"code": "undefinedField",
				"typeName": "Mutation",
				"fieldName": "storeCreditAccountCredit"
			}
		},
		{
			"message": "Variable $id is declared by storeCreditAccountCredit but not used",
			"locations": [
				{
					"line": 1,
					"column": 1
				}
			],
			"path": [
				"mutation storeCreditAccountCredit"
			],
			"extensions": {
				"code": "variableNotUsed",
				"variableName": "id"
			}
		},
		{
			"message": "Variable $creditInput is declared by storeCreditAccountCredit but not used",
			"locations": [
				{
					"line": 1,
					"column": 1
				}
			],
			"path": [
				"mutation storeCreditAccountCredit"
			],
			"extensions": {
				"code": "variableNotUsed",
				"variableName": "creditInput"
			}
		}
	]
}

So I would like to know what’s going on?

You have to use the unstable version of the api

Hello! I need to add credit feature to my store and have very basic knowledge of coding. Is there a way for me to integrate your code on my shop?

Thank you in advance for any info,

Margarita