It's not possible to retrieve a developer account API key via an API. You must obtain the key in-app, as described in this article.
You can then use this developer API key to create webhook subscriptions in your app. The OAuth access and refresh tokens you have are not able to interact with your app settings. Instead, they are only good for a client or test account.
Instead, you must either use your Developer API key ("HAPIkey") (see the Create a New Subscription section of the documentation) or create the webhook subscriptions using your developer account's UI.
i want to create webhooks.and i have only access token and refresh token which i get from oauth code,so how can i find hapikey using api so that i create webhooks.
It's not possible to retrieve a developer account API key via an API. You must obtain the key in-app, as described in this article.
You can then use this developer API key to create webhook subscriptions in your app. The OAuth access and refresh tokens you have are not able to interact with your app settings. Instead, they are only good for a client or test account.