From b815d7e881c482b9fd53111100d6fade9da71662 Mon Sep 17 00:00:00 2001 From: Chiranjeet Mishra Date: Sun, 6 Sep 2026 16:01:53 +0000 Subject: [PATCH] docs(sip): state that Vapi SIP numbers are inbound only A Vapi SIP phone number is created with a sipUri and no area code, so it has no PSTN number of its own and cannot place outbound calls. Attempts fail with call.start.error-get-transport / "Vapi Numbers Can't Dial Outbound Yet." The SIP introduction page only ever demonstrates the inbound flow, but never says outbound is unavailable, so users provision a SIP number, try an outbound call, and hit an error whose text does not explain the cause. This adds an explicit warning and points to the two paths that do support outbound. Co-Authored-By: Claude Opus 5 (1M context) --- fern/advanced/sip/sip.mdx | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/fern/advanced/sip/sip.mdx b/fern/advanced/sip/sip.mdx index 9ddd8419a..2b62c1813 100644 --- a/fern/advanced/sip/sip.mdx +++ b/fern/advanced/sip/sip.mdx @@ -8,6 +8,12 @@ slug: advanced/sip This guide shows you how to set up and test SIP calls to your Vapi assistant using any SIP client or softphone. You'll create an assistant, assign it a SIP phone number, and make a call using a SIP URI. You can also pass template variables via SIP headers. + + A Vapi SIP phone number is for **inbound calls only**. Because it is created with a `sipUri` and no area code, it has no PSTN phone number of its own, so there is no number for it to place an outbound call from. Outbound calls fail immediately with `call.start.error-get-transport` and the message `Vapi Numbers Can't Dial Outbound Yet.` + + To place outbound calls, [import a number from a supported provider](/phone-numbers/import-twilio) or [connect your own SIP trunk](/advanced/sip/sip-trunk). A SIP trunk is also what you need to call international destinations. + + ## Choose your Vapi region Use the API base URL, private key, and SIP host from the same Vapi region. Do not create a SIP phone number in one region with a SIP URI from another region.