Skip to main content

Documentation Index

Fetch the complete documentation index at: https://docs.nixflex.com/llms.txt

Use this file to discover all available pages before exploring further.

An agent is the configurable AI personality behind a phone call. One agent owns:
  • A system prompt (what the AI says, how it behaves)
  • A voice (Inworld TTS voice ID)
  • A language
  • Behaviour settings (response length, interruption sensitivity, silence handling)
  • Action configuration (transfer numbers, SMS templates)
  • An optional webhook URL for post-call data
One agent can be attached to many phone numbers. This is the multi-tenant pattern: one “dental receptionist” agent can serve hundreds of clinics, each with their own Twilio number.

​
Architecture

Agent (template/personality)
  ├── Phone Number A → Clinic 1
  ├── Phone Number B → Clinic 2
  └── Phone Number C → Clinic 3
The engine identifies which clinic is calling by the phone number that was dialled, not by which agent. The agent prompt stays the same; the per-customer context comes from the phone number record and any history Nixflex finds.

​
Configurable fields

When you POST /v1/agents, you can set:
FieldTypeDefaultPurpose
namestring"Untitled Agent"Display name in dashboard
system_promptstringemptyWhat Claude should do (see below)
welcome_messagestringgenericFirst thing the agent says on inbound calls
voice_idstring"Dennis"Inworld TTS voice
languagestring"en"Default language code
response_lengthenum"medium"short, medium, or long
interruption_sensitivityenum"medium"low, medium, high
max_call_duration_secondsint300Hard cap; engine ends call at this
silence_hangup_secondsint30Hang up if caller silent this long
record_callbooltrueRecord audio to Supabase bucket
webhook_urlstringnullWhere to POST post-call data
transfer_numberstringnullDefault destination for [TRANSFER:]
post_call_sms_templatestringnullIf set, sends this SMS after call ends
llm_modelstring"claude-haiku-4-5"LLM used during calls
temperaturefloat0.7Creativity vs predictability
fallback_messagestringsensible defaultSaid when STT confidence is too low
See the full Create Agent API reference for request and response details.

​
Writing a good system prompt

Claude is the brain. The prompt tells it who it is, what to do, and what not to do. A solid agent prompt has six sections:
1

Role

Who the agent is. “You are the front-desk assistant for Acme Dental in London.”
2

Business facts

Concrete facts the agent must know. Opening hours, address, services, prices. Never invent these.
3

Goal

What success looks like. “Book an appointment, answer a question, or transfer to the dentist if it’s clinical.”
4

Rules

Hard constraints. “Never give medical advice. Never quote prices not in this prompt. If unsure, transfer.”
5

Style

How to speak. “Warm British accent. Short sentences. One question at a time. No bullet points (you’re on a phone call).”
6

Actions

When to use built-in tags like [TRANSFER:], [SEND_SMS:], [END_CALL]. See Claude actions.
You don’t need to teach Claude how to handle interruptions, silence, language switching, or call endings. The engine injects those rules automatically. Just write the business logic.

​
Example prompt

ROLE
You are the front-desk assistant at Acme Dental, a small dental practice in Croydon, London.

BUSINESS FACTS
- Opening hours: Mon-Fri 9am-6pm, Sat 9am-1pm, closed Sun
- Address: 12 High Street, Croydon CR0 1AB
- Services: check-ups (£45), cleaning (£60), whitening (£250)
- Emergency line: transfer to +442087601234

GOAL
Book check-up appointments, answer pricing questions, transfer clinical questions to the dentist.

RULES
- Never give medical or dental advice. Transfer clinical questions.
- Quote only prices listed above. Say "let me check" if asked anything else.
- If caller sounds urgent or in pain, transfer immediately: [TRANSFER:+442087601234]
- Confirm the booking details back to the caller before ending.

STYLE
Friendly, professional, brief. Speak naturally — you're on a phone call.

ACTIONS
- To transfer: [TRANSFER:+442087601234]
- To end the call after a booking: [END_CALL]
- To text booking confirmation: [SEND_SMS: Your appointment with Acme Dental is confirmed for {date} at {time}.]

​
Listing and updating

  • GET /v1/agents — list all your agents
  • GET /v1/agents/:id — fetch one
  • PUT /v1/agents/:id — update any field
  • DELETE /v1/agents/:id — remove (calls in progress finish first)
See the API reference for full schemas.