### Answer This error indicates that the

to_number

parameter in your phone call request is empty or missing [(1) ]() . The

to_number

field is required and must contain a valid phone number . When creating a phone call, ensure your request includes a properly formatted

to_number

:

javascript
const phoneCallResponse = await client.call.createPhoneCall({
  from_number: '+14157774444',
  to_number: '+12137774445',
}) ;

, [(2) ]() The

to_number

must be a non-empty string containing the callee number [(1) ]() . Make sure you're passing a valid phone number value and not an empty string or null value.

​ To learn more, see the sources I considered: [[1] Create Phone Call](https://docs.retellai.com/api-references/create-phone-call) [[2] Retell TypeScript API Library](https://github.com/RetellAI/retell-typescript-sdk/blob/main/README.md) ​

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

### Answer When using Go High Level (GHL) workflow with Retell AI, the error you're seeing means the

to_number

field in your API request is empty [(1) ]() . In your GHL workflow's HTTP request action, verify that: 1. The

to_number

field is properly mapped to a variable containing the phone number 2. The phone number variable is not empty or null 3. The phone number is in E.164 format (e.g.,

+12137774445

) The

to_number

parameter is required and must be a non-empty string . Check your GHL workflow to ensure the phone number field is correctly populated before the API call is made. If you need to set up webhooks or custom integrations with GHL, you can configure them as long as you set up the correct webhook [(2) ]() .

​ To learn more, see the sources I considered: [[1] Create Phone Call](https://docs.retellai.com/api-references/create-phone-call) [[2] API calls](https://discord.com/channels/1186424376300679209/1227336372268957787) ​

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