Dear Vapi Support Team, I need to set a Remote-Party-ID (RPID) header for outbound calls made via your /call/phone API. My SIP trunk provider requires this header to be present in the outbound SIP INVITEs they receive from Vapi. This is necessary for proper call routing, caller ID presentation, and to avoid call setup failures (e.g., 403 Forbidden errors). The Remote-Party-ID header needs a specific value, for example: "Display Name" ;party=calling;screen=yes;privacy=off Could you please provide explicit instructions or documentation on how to include this custom Remote-Party-ID SIP header, with its full string value, in the outbound SIP INVITE generated by Vapi when using the /call/phone API? Is there a specific field in the API request body designed for custom SIP headers, or another method available? This capability is crucial and is currently blocking our integration. Thank you for your assistance.

Thanks for reaching out! I couldn't find enough info in the docs about setting a custom Remote-Party-ID (RPID) SIP header for outbound calls via the

/call/phone

API. Since this is blocking your integration, I'm escalating your request to a human on our team who can provide a definitive answer. We'll get back to you as soon as possible! For reference, you can check the [SIP integration docs](https://docs.vapi.ai/advanced/sip) and [API reference](https://docs.vapi.ai/api-reference/calls/create), but I didn't see anything specific about custom SIP headers. Hang tight—we'll follow up soon!

Unfortunately, Vapi's /call/phone API does not currently support adding custom SIP headers like Remote-Party-ID. The API schema only accepts standard call parameters (assistant, phone number, customer) but has no mechanism for custom SIP header injection. You can raise an feature request for it over here: https://roadmap.vapi.ai