Using this API call we can check if an address is whitelisted for a specific paymaster address.

  const sponsorAddress = ('0x8350355c08aDAC387b443782124A30A8942BeC2e');
	const accountAddress = ('0xE008De2fc3D19B51dC6Ff5379Af9b970fB21E43D');
	const chainId = 80001;
	const api_key = '';
	const returnedValue = await fetch('https://arka.etherspot.io/checkWhitelist', {
		method: 'POST',
		headers: {
			'Accept': 'application/json',
			'Content-Type': 'application/json',
		},
		body: JSON.stringify({ "params": [sponsorAddress, accountAddress, chainId, api_key] })
	})
		.then((res) => {
			return res.json()
		}).catch((err) => {
			console.log(err);
			// throw new Error(JSON.stringify(err.response))
		});
	console.log('Value returned: ', returnedValue);

You should see an output like this if the address has been whitelisted:

Value returned:  { message: 'Already added' }