> ## Documentation Index
> Fetch the complete documentation index at: https://docs.mrassistant.ai/llms.txt
> Use this file to discover all available pages before exploring further.

# Transfer Call

> Transfer a call to another number or SIP endpoint.

Supports two transfer types:
- cold: Direct transfer, agent disconnects immediately
- warm: Agent provides context before connecting (requires additional orchestration)

The transfer_to parameter must be in one of these formats:
- tel:+15105550100 (phone number)
- sip:user@domain.com (SIP endpoint)
- sip:+15105550100@sip.telnyx.com (phone via SIP URI)



## OpenAPI

````yaml https://api.mrassistant.ai/openapi.json post /calls/{call_id}/transfer
openapi: 3.1.0
info:
  title: Backend - Multilingual Voice Agent System
  description: FastAPI backend for multilingual voice agents with tool use
  version: 1.0.0
servers: []
security: []
paths:
  /calls/{call_id}/transfer:
    post:
      tags:
        - calls
      summary: Transfer Call
      description: >-
        Transfer a call to another number or SIP endpoint.


        Supports two transfer types:

        - cold: Direct transfer, agent disconnects immediately

        - warm: Agent provides context before connecting (requires additional
        orchestration)


        The transfer_to parameter must be in one of these formats:

        - tel:+15105550100 (phone number)

        - sip:user@domain.com (SIP endpoint)

        - sip:+15105550100@sip.telnyx.com (phone via SIP URI)
      operationId: transfer_call_calls__call_id__transfer_post
      parameters:
        - name: call_id
          in: path
          required: true
          schema:
            type: string
            format: uuid
            title: Call Id
      requestBody:
        required: true
        content:
          application/json:
            schema:
              $ref: '#/components/schemas/TransferCallRequest'
      responses:
        '200':
          description: Successful Response
          content:
            application/json:
              schema: {}
        '422':
          description: Validation Error
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/HTTPValidationError'
      security:
        - HTTPBearer: []
components:
  schemas:
    TransferCallRequest:
      properties:
        transfer_to:
          type: string
          title: Transfer To
          description: 'Destination: tel:+15105550100 or sip:user@domain.com'
        transfer_type:
          type: string
          pattern: ^(cold|warm)$
          title: Transfer Type
          description: 'Transfer type: cold or warm'
          default: cold
        play_dialtone:
          type: boolean
          title: Play Dialtone
          description: Play dial tone during transfer
          default: false
      type: object
      required:
        - transfer_to
      title: TransferCallRequest
      description: Request to transfer a call.
    HTTPValidationError:
      properties:
        detail:
          items:
            $ref: '#/components/schemas/ValidationError'
          type: array
          title: Detail
      type: object
      title: HTTPValidationError
    ValidationError:
      properties:
        loc:
          items:
            anyOf:
              - type: string
              - type: integer
          type: array
          title: Location
        msg:
          type: string
          title: Message
        type:
          type: string
          title: Error Type
        input:
          title: Input
        ctx:
          type: object
          title: Context
      type: object
      required:
        - loc
        - msg
        - type
      title: ValidationError
  securitySchemes:
    HTTPBearer:
      type: http
      scheme: bearer

````