Can I use the RTP rail to pull funds from an external bank account?
The Clearing House designed RTP to allow outbound credits only and did not include any "pull" feature.

How can I determine whether a bank is enabled for RTP services?
Partners can use the GET /v1/directory endpoint to search for banks that participate in RTP services. You can also filter by variables such as routing number, bank name, etc. The endpoint response will provide a list of RTP services in the receiveServices array. Please note that although a bank may indicate that it receives a particular RTP service, this does not guarantee that the account receiving your RTP payment is eligible.