Nixflex - AI Voice Platform for Building AI Phone Agents

Import phone number

curl --request POST \
  --url https://api.nixflex.com/v1/phone-numbers

<?php

$curl = curl_init();

curl_setopt_array($curl, [
  CURLOPT_URL => "https://api.nixflex.com/v1/phone-numbers",
  CURLOPT_RETURNTRANSFER => true,
  CURLOPT_ENCODING => "",
  CURLOPT_MAXREDIRS => 10,
  CURLOPT_TIMEOUT => 30,
  CURLOPT_HTTP_VERSION => CURL_HTTP_VERSION_1_1,
  CURLOPT_CUSTOMREQUEST => "POST",
]);

$response = curl_exec($curl);
$err = curl_error($curl);

curl_close($curl);

if ($err) {
  echo "cURL Error #:" . $err;
} else {
  echo $response;
}

package main

import (
	"fmt"
	"net/http"
	"io"
)

func main() {

	url := "https://api.nixflex.com/v1/phone-numbers"

	req, _ := http.NewRequest("POST", url, nil)

	res, _ := http.DefaultClient.Do(req)

	defer res.Body.Close()
	body, _ := io.ReadAll(res.Body)

	fmt.Println(string(body))

}

require 'uri'
require 'net/http'

url = URI("https://api.nixflex.com/v1/phone-numbers")

http = Net::HTTP.new(url.host, url.port)
http.use_ssl = true

request = Net::HTTP::Post.new(url)

response = http.request(request)
puts response.read_body

POST

phone-numbers

Import phone number

curl --request POST \
  --url https://api.nixflex.com/v1/phone-numbers

<?php

$curl = curl_init();

curl_setopt_array($curl, [
  CURLOPT_URL => "https://api.nixflex.com/v1/phone-numbers",
  CURLOPT_RETURNTRANSFER => true,
  CURLOPT_ENCODING => "",
  CURLOPT_MAXREDIRS => 10,
  CURLOPT_TIMEOUT => 30,
  CURLOPT_HTTP_VERSION => CURL_HTTP_VERSION_1_1,
  CURLOPT_CUSTOMREQUEST => "POST",
]);

$response = curl_exec($curl);
$err = curl_error($curl);

curl_close($curl);

if ($err) {
  echo "cURL Error #:" . $err;
} else {
  echo $response;
}

package main

import (
	"fmt"
	"net/http"
	"io"
)

func main() {

	url := "https://api.nixflex.com/v1/phone-numbers"

	req, _ := http.NewRequest("POST", url, nil)

	res, _ := http.DefaultClient.Do(req)

	defer res.Body.Close()
	body, _ := io.ReadAll(res.Body)

	fmt.Println(string(body))

}

require 'uri'
require 'net/http'

url = URI("https://api.nixflex.com/v1/phone-numbers")

http = Net::HTTP.new(url.host, url.port)
http.use_ssl = true

request = Net::HTTP::Post.new(url)

response = http.request(request)
puts response.read_body

Attaches a phone number you already own to one of your agents. Nixflex supports Twilio and Telnyx. You do not choose the carrier with a field — it is inferred from the credentials you send. Send Twilio credentials and the number is imported as a Twilio number; send a Telnyx API key and it is imported as a Telnyx number.

Existing integrations need no changes. If you only ever send twilio_sid and twilio_token, nothing about this endpoint has changed for you.

Twilio

curl -X POST https://api.nixflex.com/v1/phone-numbers \
  -H "Authorization: Bearer KEY_ID:KEY_SECRET" \
  -H "Content-Type: application/json" \
  -d '{
    "phone_number": "+447446466847",
    "twilio_sid":   "ACxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx",
    "twilio_token": "your_twilio_auth_token",
    "agent_id":     "agent_125207e452f8714a"
  }'

Field	Type	Required	Notes
`phone_number`	string	Yes	E.164 format (`+44...`). Must already exist in your Twilio account
`twilio_sid`	string	Yes	Your Twilio Account SID, format `AC` + 32 hex characters
`twilio_token`	string	Yes	Your Twilio Auth Token
`agent_id`	string	Yes	Must be an agent you own
`custom_prompt`	string	No	Per-number prompt override. Max 8000 characters

Nixflex points the number’s voice, SMS and status webhooks at the engine for you.

Importing replaces the existing webhooks on the Twilio number. If another system uses this number, it will stop receiving calls and SMS.

Telnyx

Telnyx works differently, and the difference matters. On Twilio, the webhook URL lives on the number. On Telnyx, the webhook lives on a TeXML Application, and numbers are assigned to that application. Nixflex never creates the application — you create it once in your Telnyx portal, then every number you assign to it is handled by Nixflex.

Create a TeXML Application in your Telnyx portal

Set its voice webhook URL to https://api.nixflex.com/telnyx-voice, method POST, webhook API version 2. Copy the application’s ID — that is your telnyx_connection_id.

Check the codec settings

Enable G711U. Turn G722 / HD Voice off. The engine speaks mu-law only; a call that negotiates another codec will connect but carry no usable audio.

Import the number

Nixflex assigns the number to your TeXML application for you.

curl -X POST https://api.nixflex.com/v1/phone-numbers \
  -H "Authorization: Bearer KEY_ID:KEY_SECRET" \
  -H "Content-Type: application/json" \
  -d '{
    "phone_number":         "+443301901028",
    "telnyx_api_key":       "KEY0123456789...",
    "telnyx_connection_id": "2512345678901234567",
    "agent_id":             "agent_125207e452f8714a"
  }'

Field	Type	Required	Notes
`phone_number`	string	Yes	E.164 format. Must already exist in your Telnyx account
`telnyx_api_key`	string	Yes	A Telnyx API key with access to the number
`telnyx_connection_id`	string	Yes	The ID of your TeXML Application
`agent_id`	string	Yes	Must be an agent you own
`custom_prompt`	string	No	Per-number prompt override. Max 8000 characters

camelCase works everywhere too: phoneNumber, twilioSid, twilioToken, telnyxApiKey, telnyxConnectionId, agentId, customPrompt.

What Telnyx numbers support today

	Status
Inbound calls	Yes
Recording	Yes
Cold and warm transfer	Yes
Concurrency limits	Yes
Booking, custom functions, analysis, webhooks	Yes
Live Monitor	Yes
Inbound SMS and auto-reply	Yes
Sending SMS	Yes
SMS delivery status	Yes
SMS campaigns	Yes
Outbound calls	Yes
Outbound recording	Yes
Keypad input (DTMF)	Yes
Carrier voicemail detection (AMD)	Yes

Telnyx numbers support the same feature set as Twilio numbers, including SMS campaigns and delivery receipts. You do not need to pick a carrier based on features - pick on price, coverage, and whichever account you already have.

Response

201 Created:

{
  "phone_number": {
    "phone_number": "+447446466847",
    "agent_id": "agent_125207e452f8714a",
    "provider": "twilio",
    "twilio_number_sid": "PN451e0ddf654327e36baab58dfbcd30d6",
    "inbound_enabled": true,
    "outbound_enabled": true
  }
}

A Telnyx import returns "provider": "telnyx" and telnyx_number_id instead of twilio_number_sid.

Errors

Both carriers

Code	HTTP	Cause
`missing_field`	400	A required field is empty
`invalid_phone_format`	400	Not E.164 format
`custom_prompt_too_long`	400	Over 8000 characters
`agent_not_found`	404	`agent_id` does not exist
`agent_not_owned`	403	The agent belongs to a different API key
`number_already_imported`	409	Already attached to an agent

Twilio

Code	HTTP	Cause
`invalid_twilio_sid`	400	SID does not match `AC` + 32 hex
`twilio_invalid_credentials`	401	SID and token rejected by Twilio
`twilio_auth_failed`	401	Twilio authentication error
`number_not_in_twilio`	404	Number not in your Twilio account

Telnyx

Code	HTTP	Cause
`telnyx_invalid_credentials`	401	API key rejected by Telnyx
`number_not_in_telnyx`	404	Number not in your Telnyx account
`telnyx_assign_failed`	400	Could not assign the number to that TeXML application — check the ID
`telnyx_error`	500	Telnyx returned an unexpected error

Use case: reseller onboarding

// 1. Buy a number from your Twilio account
const twilio = require('twilio')(YOUR_TWILIO_SID, YOUR_TWILIO_TOKEN);
const available = await twilio.availablePhoneNumbers('GB').local.list({ limit: 1 });
const purchased = await twilio.incomingPhoneNumbers.create({
  phoneNumber: available[0].phoneNumber
});

// 2. Attach it to your Nixflex agent
await fetch('https://api.nixflex.com/v1/phone-numbers', {
  method: 'POST',
  headers: {
    'Authorization': `Bearer ${NIXFLEX_KEY_ID}:${NIXFLEX_KEY_SECRET}`,
    'Content-Type': 'application/json'
  },
  body: JSON.stringify({
    phone_number: purchased.phoneNumber,
    twilio_sid: YOUR_TWILIO_SID,
    twilio_token: YOUR_TWILIO_TOKEN,
    agent_id: 'agent_your_template'
  })
});

​Twilio

​Telnyx

​Response

​Errors

​Use case: reseller onboarding

Twilio

Telnyx

Response

Errors

Use case: reseller onboarding