### Answer Yes, you can use custom SIP headers to set dynamic variables for inbound calls received via transfer [(1) ]() . Custom SIP headers that start with

sip.h.x-

will be converted to dynamic variables after removing the prefix . For example, a header

sip.h.x-caller: abc

becomes the dynamic variable

x-caller: abc

. However, there's an important limitation to be aware of: based on community discussions, there appears to be a known issue when transferring calls between agents where custom SIP headers may not properly pass through to the transferred (inbound) agent when certain settings are enabled [(2) ]() . Users have reported that custom SIP headers appear in the parent call's webhook response but not in the forwarded call's webhook response under specific configurations . The header format needs to end with

-Header

(for example,

X-uuid-Header

) for it to work properly in transfer scenarios .

​ To learn more, see the sources I considered: [[1] Receive calls](https://docs.retellai.com/deploy/inbound-call) [[2] Why can't we pass metadata or dynamic variables to a transfered call ?](https://discord.com/channels/1186424376300679209/1388693750213116004) ​

Feel free to tag @AI Evy with additional questions. I also appreciate feedback, it helps me improve.