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fix: expose phone number provider and add outbound call guidance#15

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tasker/PRO-1050-fix-mcp-outbound-validation
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fix: expose phone number provider and add outbound call guidance#15
vapi-tasker[bot] wants to merge 1 commit intomainfrom
tasker/PRO-1050-fix-mcp-outbound-validation

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@vapi-tasker vapi-tasker bot commented Mar 23, 2026

Summary

Fixes the cryptic call.start.error-get-transport — Vapi Numbers Can't Dial Outbound Yet error that MCP users encounter when using create_call with a Vapi-provisioned phone number.

Root cause: The MCP server did not expose the phone number provider field, so clients had no way to determine which numbers support outbound dialing. Additionally, tool descriptions gave no guidance about the Twilio/Vonage requirement for outbound calls.

Changes:

  • Add provider field to PhoneNumberOutputSchema and transformPhoneNumberOutput so MCP clients can see whether a number is vapi (inbound-only), twilio, or vonage (outbound-capable)
  • Update create_call tool description to clearly state that outbound calls require a Twilio or Vonage imported phone number
  • Update CallInputSchema.phoneNumberId description with guidance about which phone numbers work for outbound

Test plan

  • Added 6 unit tests covering all three fixes:
    • Schema has provider field
    • Transformer exposes provider for vapi, twilio, and vonage numbers
    • Transformer defaults to "unknown" when provider is missing
    • phoneNumberId description mentions Twilio, Vonage, and outbound
  • All existing mock tests pass (no regressions)
  • Source files compile cleanly with tsc --noEmit

Linear issue

PRO-1050


Generated with Claude Code

Customers using create_call with a Vapi-provisioned phone number get a
cryptic transport error because Vapi numbers are inbound-only. This
change surfaces the provider field so MCP clients can identify which
numbers support outbound dialing, and updates tool descriptions to
clearly communicate the Twilio/Vonage requirement.

Changes:
- Add provider field to PhoneNumberOutputSchema and transformer
- Update create_call tool description with outbound requirements
- Update CallInputSchema.phoneNumberId with provider guidance
- Add 6 unit tests covering all three fixes

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
@vapi-tasker vapi-tasker bot closed this Mar 23, 2026
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