I am looking for a way to register a webhook that will fire up when adding or changing notes on my contacts.
I looked at the doc and I did not find anything.
It’s not currently possible to subscribe to a web hook based on note/engagement creations. If you have the inclination, I would definitely encourage you to check out the Ideas Forum on the HubSpot Community. There, you can post/vote on ideas for the product to be seen by HubSpotters, partners, and other customers alike.