> For a complete page index, fetch https://docs.synthflow.ai/llms.txt. For full documentation content, fetch https://docs.synthflow.ai/llms-full.txt.

## Phone numbers API: Five9 and RingCX

You can now import [Five9](/sip-with-five9) and [RingCX](/sip-with-ringcx) numbers through the [`POST /custom-numbers`](/api-reference/platform-api/phone-numbers/create-custom-number) endpoint. Synthflow sets their SIP domain automatically.