21200: Calls Resource

This error points to a problem with a request to the Calls resource. When you create a call, include to and from, and provide url, twiml, or applicationSid so Twilio can execute the call.

• The request omitted the required to parameter or from parameter.
• The request did not include url, twiml, or applicationSid to provide call instructions.
• The from value is not a Twilio phone number or a verified outgoing caller ID, or to is a phone number while from is not.
• The request used an unsupported value for method, fallbackMethod, or statusCallbackMethod. These parameters only accept GET or POST.
• The request included an invalid url or callback URL. The call url must be an absolute URL, and statusCallback URLs must contain a valid hostname.

• Send the call request as application/x-www-form-urlencoded and confirm that all required parameters are present.
• Provide a valid url, inline twiml, or a valid applicationSid so Twilio has instructions for the call.
• If you are calling a phone number, format to and from in E.164 and use a Twilio number or verified outgoing caller ID for from.
• Use only GET or POST for method parameters, and make sure every webhook URL is publicly reachable by Twilio.
• Review your Voice logs and the Request Inspector in Twilio Console to identify the exact parameter or webhook that failed.

• Call resource API reference
• Make outbound phone calls
• Troubleshooting Outgoing Twilio Programmable Voice Calls