Nixflex - AI Voice Platform for Building AI Phone Agents

An outbound call is one where Nixflex calls a number for you: appointment reminders, no-show follow-ups, lead qualification, renewal nudges, surveys - anything where the agent reaches out first.

Your agent’s instructions are for inbound calls only. They are not used on outbound calls.Every outbound call runs on its own prompt - the one you send with the call, or the one saved on the campaign. The agent’s inbound instructions and the number’s business profile are not loaded. Write the outbound prompt as if the agent knows nothing: who it is calling on behalf of, why it is calling, what to say, when to stop.

Think of each campaign as its own outbound agent

You do not write a fresh prompt for every call. You write one per scenario, save it as a campaign, and reuse it.

Appointment reminder

“Confirm tomorrow’s appointment. If they cannot make it, offer to rebook.”

No-show follow-up

“They missed today’s appointment. Be kind, offer the next available slot.”

Promotion

“Tell existing customers about this month’s offer. No hard sell.”

Renewal nudge

“Their plan ends this month. Ask if they want to continue.”

Review request

“Thank them for their visit and ask for a quick review.”

Lead follow-up

“They filled in the form. Find out what they need and book a call.”

Each one is a campaign in the dashboard: a name, an agent, a from-number, the prompt, and the recipient list. Write the prompt properly once - the same seven-section shape as any agent, see Writing a good agent prompt - and it is saved.

Create the campaign once

Dashboard -> Outbound calls -> New campaign. Name it after the scenario, choose the agent and from-number, write the prompt, add recipients, launch.

Reuse it next time

Open the campaign and choose reuse. The prompt, agent and from-number come back. Replace the recipients, change a date or a detail if needed, launch again.

Build a small library

Five or six campaigns cover most businesses. After that, running a campaign is a two-minute job - pick the scenario, paste the numbers, go.

Through the API, the same idea: keep your scenario prompts in your own system and send the right one with each call or batch.

Trigger one call

curl -X POST https://api.nixflex.com/v1/calls/outbound \
  -H "Authorization: Bearer KEY_ID:KEY_SECRET" \
  -H "Content-Type: application/json" \
  -d '{
    "agent_id": "agent_125207e452f8714a",
    "to_number": "+447386172392",
    "prompt": "You are calling on behalf of Acme Dental. Remind the person about their appointment tomorrow at 2pm and ask them to confirm they can still attend.",
    "from_number": "+447700900123"
  }'

Field	Required	What it does
`agent_id`	Yes	Which agent makes the call - it supplies the voice, language and base behaviour
`to_number`	Yes	Who to call, in E.164 format
`prompt`	Yes	The whole brief for this call. At least 10 characters; a shorter prompt makes the agent apologise and end the call
`from_number`	No	Which of the agent’s numbers to call from. Sets the caller ID and the per-number voice. Omit it and the agent’s first outbound-enabled number is used
`dynamic_vars`	No	Your own values, written into the prompt as `{{name}}`. See Variables
`post_call_sms_enabled`, `post_call_sms_template`	No	Send a text after this call, overriding the agent’s setting for this call only
`campaign_id`	No	Attach this call to a batch campaign

The response returns a call_id straight away. The call itself happens in the background: your carrier dials, the agent waits for pickup, then the conversation runs.

What instructions does the agent follow on an outbound call?

Exactly three things, in this order:

Base behaviour - how to speak on the phone, interruptions, silence, endings. Built in.
Your prompt - sent with the call or saved on the campaign, as a CALL PURPOSE block.
What is on file about the person - see below.

Not included: the agent’s inbound instructions, and the number’s business profile. If the agent needs the business name, opening hours or a policy, put it in the outbound prompt.

What happens on the receiving end

Your carrier dials

From the number you chose, as an ordinary phone call.

Voicemail is detected

The agent listens to the first thing it hears. An answering machine ends the call - it does not talk to a recording. Switch on Leave a Voicemail Message and it speaks your message first. Your carrier’s own detection can run as well (amd_enabled): it hangs up earlier and cannot leave a message, at a small charge per answered call. See Voicemail detection.

A person answers

The agent waits a moment, introduces itself and states why it is calling.

The conversation

From here it behaves like any call: the person’s speech becomes text, the agent decides what to say, a natural voice speaks it. Interruptions and silence are handled. The agent can transfer, text, take keypad input or book, if your prompt tells it when.

The agent already knows the person it is calling

Before the call connects, Nixflex looks up what is on file for that number on this business number and puts it into the agent’s instructions. No CSV wiring, no placeholders.

Detail	Where it comes from
Name, email, phone, location, reference, preference	You, through the API, an import or the dashboard - or learned when the person stated it on an earlier call
Open item	Anything still outstanding for that person after a previous call

Without it (other platforms): you upload a CSV with a dozen columns and wire each into the prompt. Miss one and the prompt breaks. With it (Nixflex): you upload numbers and one prompt. The agent already has Sarah’s name, email and reference, and confirms them with her before doing anything.

Past outcomes are never injected - by design. The agent is told what is on file about the person, never what happened on a previous call. Feeding a past booking into a call once made an agent confirm an appointment it had not made. The agent confirms details with the person and checks the calendar itself.

Details are scoped to the business number that is calling, so one customer’s records never surface on another customer’s number. You can also send details live for one call from your own system with the pre-call gate. See Caller context. Yes, on outbound calls. If the number it calls answers with “press 1 for sales”, the agent can navigate it. Your prompt teaches it when to use [IVR], [PRESS: 2] and [IVR_END], and the agent’s Phone menu wait setting says how long to hold for a real person before giving up. While it waits, silence timers pause so hold music never ends the call. See IVR navigation.

Batch campaigns

To call many numbers, create a campaign. One request queues every call.

curl -X POST https://api.nixflex.com/v1/calls/batch \
  -H "Authorization: Bearer KEY_ID:KEY_SECRET" \
  -H "Content-Type: application/json" \
  -d '{
    "agent_id": "agent_125207e452f8714a",
    "name": "Tuesday reminders",
    "prompt": "You are calling on behalf of Acme Dental to confirm tomorrow's appointment for {{first_name}} at {{appointment_time}}.",
    "recipients": [
      { "phone_number": "+447111000001", "first_name": "Sarah", "appointment_time": "2pm" },
      { "phone_number": "+447111000002", "first_name": "Tom",   "appointment_time": "3:30pm" }
    ],
    "schedule_type": "now"
  }'

Every extra column on a recipient becomes a variable for that call - {{first_name}}, {{appointment_time}} - and is also handed to the agent as context even if the prompt never mentions it.
schedule_type is now or schedule; with schedule, give the date and time to start.
Calls run inside your account’s concurrency limit - the number of calls allowed at once per API key, shared with inbound, 10 by default - so a campaign of 500 does not flood your carrier.
In the dashboard, campaigns use numbers added in the dashboard; numbers imported through the API are run through the API.

See Batch create and Launch for the full schema.

What happens if nobody answers?

The call ends without a conversation and the outcome is recorded on the call record and sent to your webhook as ended_reason - for example voicemail_detected when a machine answered, or callee_hangup when the person hung up. No answer and busy are recorded too. In a campaign, each recipient’s outcome is tracked separately, so you can see who was reached.

Voicemail behaviour

Message configured: the agent speaks exactly that message, then hangs up.
Nothing configured: the agent hangs up without speaking.
The call is recorded with voicemail_detected and billed per second like any other connected call.
Where the message lives depends on how the number was imported: on the agent for dashboard-added numbers, on the number for API-imported ones. See Voicemail detection.

Useful for

Appointment reminders the day before Â· No-show follow-ups Â· Lead qualification after a form submission Â· Renewal nudges Â· Satisfaction and review requests Â· Re-engaging cold contacts Â· Debt collection, with proper compliance on your side.

Outbound calling has rules - TCPA in the US, Ofcom in the UK, consent requirements elsewhere. Make sure you have the right to call every number you upload. Nixflex provides the infrastructure; compliance is yours.

Create outbound call - every field
Batch create - campaigns through the API
Variables - dynamic_vars and recipient columns
Voicemail detection - both layers, and the message
IVR navigation - getting through phone menus
Inbound calls - the other direction

Get started

Guides

Best practices

Core concepts

In-call actions

Features

Bring your own

SMS

Reference

Outbound calls

Think of each campaign as its own outbound agent

Appointment reminder

No-show follow-up

Promotion

Renewal nudge

Review request

Lead follow-up

Trigger one call

What instructions does the agent follow on an outbound call?

What happens on the receiving end

The agent already knows the person it is calling

Can the agent get through a phone menu?

Batch campaigns

What happens if nobody answers?

Voicemail behaviour

Useful for

​Think of each campaign as its own outbound agent

Appointment reminder

No-show follow-up

Promotion

Renewal nudge

Review request

Lead follow-up

​Trigger one call

​What instructions does the agent follow on an outbound call?

​What happens on the receiving end

​The agent already knows the person it is calling

​Can the agent get through a phone menu?

​Batch campaigns

​What happens if nobody answers?

​Voicemail behaviour

​Useful for

​Related

Think of each campaign as its own outbound agent

Trigger one call

What instructions does the agent follow on an outbound call?

What happens on the receiving end

The agent already knows the person it is calling

Can the agent get through a phone menu?

Batch campaigns

What happens if nobody answers?

Voicemail behaviour

Useful for

Related