Yes, currently the HTTP API is the only way to send data from Clay to Attio. You can use our HTTP API feature to connect to any external tool that you have API access to. If a native integration hasn't been built for a tool you're looking to connect with, you can access any API endpoint using a custom HTTP/API call. To use Clay programmatically, you can process your data within Clay and then use our HTTP API integration to pass output data to other services like Attio.
Sources:FAQ | Clay.comReply.io - Clay University