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.

Nixflex is a real-time voice AI platform. You connect your Twilio number, give Claude a prompt, and your phone agent is live. Inbound and outbound calls, SMS, transfers, post-call analysis, batch campaigns — all behind one API. Built for developers embedding voice agents into SaaS apps.

​
Why Nixflex

Sub-second response

First audio in ~500ms. AssemblyAI / Deepgram for STT, Claude Haiku 4.5 for reasoning, Inworld TTS for voice.

Bring your own Twilio

Multi-tenant from day one. Each customer connects their own Twilio account — you keep full control of phone numbers and billing.

Tag-based actions

Claude triggers transfers, SMS, and call endings through prompt tags. No webhook orchestration needed for built-in actions.

History-aware calls

Outbound calls automatically pull past call summaries for the recipient and inject them into the agent’s prompt. Your agent remembers customers across calls.

​
Get started

Quickstart

Make your first call in under five minutes.

Authentication

Generate API keys and authenticate requests.

Create an agent

Configure prompts, voice, language, and actions.

API reference

Every endpoint with parameters, examples, and error codes.

​
How it works

A call moves through the engine like this:
  1. Caller dials your Twilio number (or you trigger an outbound call via API).
  2. Twilio streams audio to Nixflex over WebSocket.
  3. Speech-to-text converts what the caller says into text in real time.
  4. Claude reasons over the conversation and decides what to say or do next.
  5. Text-to-speech turns the reply into natural voice and streams it back to the caller.
  6. After the call ends, Nixflex runs post-call analysis (summary, sentiment, custom data extraction) and fires your webhook.
You configure the agent’s behaviour with a system prompt and a handful of settings. Everything else — audio handling, interruption detection, language matching, voicemail filtering — is handled by the engine.

​
Built-in capabilities

Inbound + outbound calls

Cold and warm transfers

Mid-call and post-call SMS

Voicemail detection (AMD + Deepgram)

Batch voice + SMS campaigns

Auto language detection (15+ languages)

Post-call summary, sentiment, data extraction

Custom functions (tools Claude can call mid-call)

​
Pricing

Pay-as-you-go from $0.08 per minute of voice. SMS billed per message at your Twilio rate. See pricing details for plans and volume discounts.

​
Need help?

Email support@nixflex.com or check the error reference for common issues.