40158: Call Instruction does not have a valid 'status_callback_url' parameter

This error occurs when your Assignment Callback returns an instruction of call and includes a status_callback_url value that is not a valid URL string. status_callback_url is optional for a Call Instruction, but if you include it, provide a valid callback URL so Twilio can send call status updates for the worker call.

• You sent status_callback_url as an empty string.
• You sent status_callback_url with the wrong data type instead of a URL string.
• You sent a malformed status_callback_url value that is not a complete http:// or https:// URL.

• Set status_callback_url to a well-formed http:// or https:// URL string in the JSON response for your "instruction":"call" Assignment Callback.
• If you do not need status callbacks for the worker call, omit status_callback_url instead of sending an empty value.
• Validate your Assignment Callback payload before you return it so status_callback_url is serialized as a string and contains the exact endpoint Twilio should request when the worker call completes.
• Review the full Call Instruction payload and confirm related fields such as url, from, and to are also valid for the outbound worker call.

• Handling Assignment Callbacks
• How TaskRouter Works
• TaskRouter REST API Reference