Skip to main content
Most voice platforms make you build a flow chart - dragging boxes and drawing arrows for every turn a call could take. Nixflex does not work that way, and you do not need it to. You guide the agent by describing what should happen in each situation, in plain English, inside your instructions. Think of it like briefing a new member of your team: what callers ask for, what to collect, what to say, and what to do next. The clearer the description, the more reliably the agent follows it.

​
Start with the scenarios, not the wording

Before writing anything, list the situations your agent will actually face. Almost every phone agent meets the same core set: For each one, answer four questions: what does the caller want → what should the agent ask → what should it say → what should it do? That is your conversation logic. The wording comes after.

​
The pattern: “if this, do that”

Every scenario rule has the same shape:
If the caller says or does something, then respond or act in a specific way.
If the caller asks about prices, tell them a check-up is 50 pounds and a cleaning is 70 pounds.
If the caller asks to speak to a person, transfer them to reception.
If you do not know the answer, say you will pass the message on and have someone call them back. Never invent information.
Each rule is one line. Stack as many as you need and you have described the whole call, without a single diagram. The exact wording matters far less than being unambiguous about the situation, the information to collect, the reply, and the action.

​
A full example

A complete scenario block for a dental clinic. Drop a section like this into your instructions and the agent handles the call as written:
That is a conversation flow written as sentences instead of boxes.

​
Write the order for anything with steps

When a scenario has several steps, write them in order. The agent works through them and will not jump ahead, because you said what comes first:
When booking an appointment:
  1. Ask for the caller’s full name.
  2. Ask which day they would prefer.
  3. Repeat the day back to confirm it.
  4. Use the booking function to reserve the slot.
  5. Tell the caller the confirmed day and time.
Never assume the agent knows which detail is required or which step comes first. If the order matters, write the order down.

​
Be specific

The agent can only follow what you actually wrote. Vague
Handle cancellations.
Specific
If the caller wants to cancel, take their full name and the appointment day, confirm the details back to them, then offer to have reception call to rebook.
The second version says when the rule applies, what to collect, what to confirm and what happens next. If a behaviour matters, spell it out.

​
Let your rules trigger actions

Scenario rules become powerful when they decide when to use an action or a custom function:
If the caller asks whether a slot is free, use the availability function before answering.
If the caller confirms the booking, text them the details: [SEND_SMS: Your appointment is confirmed for the day and time we agreed.]
The rule decides when. The action or function does the work.

​
What you do not need to write

Skip the plumbing. The platform already handles it on every call:
  • Interruptions - the agent stops and listens when the caller cuts in
  • Silence - it checks whether the caller is still there, then ends politely
  • Language - it follows the caller between languages
  • Numbers, dates and email addresses - spoken details are written out properly
  • Voicemail on outbound calls - it recognises an answering machine and acts on it
Spend your instructions on the part only you know: what to say, what to collect, what to ask, what to do, what never to do, when to transfer, and what happens when information is unavailable.

​
Make the rules that matter stick

For the rules you cannot afford to get wrong - a required disclaimer, a hard “never do this”:
  • Put them near the top of your instructions
  • Keep each one short and direct - one instruction, not a paragraph
  • Use plain, explicit wording
Instead of “Try not to give customers information that may be incorrect”, write “Never invent information. If you do not know, tell the caller someone from the team will follow up.”
A written rule guides the agent; it is not a technical lock. For anything critical - compliance wording, permissions, actions that must never happen - do not rely on the instructions alone. Keep the rule short, put it early, and test it before you go live.

​
What a finished prompt looks like

Everything above goes into one set of instructions, organised under headings. Use ## headings inside the prompt - the model uses them to find the right rule quickly, and they are never spoken aloud:
See Writing a good agent prompt for a complete filled-in version you can copy.

​
Can ChatGPT or Claude write my agent instructions?

Yes, and for most agents we recommend it. You do not need to be an expert prompt writer - you need to know your business. Give a capable model your business facts and your scenario list, and ask it to turn them into instructions for a voice agent.
1

Describe your business

Services, prices, opening hours, address, booking process, who to transfer to, and anything the agent must never say.
2

List your scenarios

Use the table at the top of this page as a starting point, then add the situations specific to you - the ones you cannot afford to get wrong.
3

Ask for a voice-agent prompt

Say explicitly that it will be spoken aloud on a phone call. This is the step people skip, and it is the one that matters most - chat writing makes an agent that lectures the caller.
4

Check what it wrote

Read every fact. A model will happily invent a price, an opening time or a policy to fill a gap. You are the source of truth, not the model.
5

Test it on real calls

Normal requests, odd ones, interruptions, an impatient caller.
6

Fix the rule, not the symptom

When the agent gets something wrong, find the scenario rule that was missing or unclear and improve it. Do not work around it.
A starting message you can copy:
An LLM-written prompt is a strong first draft, not a finished agent. The value is in what you add after the first few real calls.

​
Scenario starters by industry

Copy the set closest to your business and change the details. Dental or medical practice
Book, cancel or move an appointment - collect the full name and preferred day. Quote only listed treatment prices. Never give clinical advice; transfer anything medical. If the caller sounds in pain or says it is an emergency, transfer immediately. Confirm the day and time back before ending.
Restaurant
Take a table booking - party size, day, time, name and a contact number. Answer opening hours, address and parking from the facts. Take dietary requirements as a note, never promise a dish is safe. Large groups go to the manager. If fully booked, offer the nearest alternative times.
Estate or letting agent
Book a viewing - property address, preferred day, name and number. Answer only listed details: price, bedrooms, availability date. Never negotiate or discuss offers; take a message for the agent. Maintenance calls from existing tenants go to the property manager.
Salon, clinic or garage
Book a service - the service wanted, preferred day, name and number. Quote only listed prices and say how long each takes. Cancellations inside 24 hours go to a person. If a caller wants something you do not offer, say so plainly and take a message.