APIs for AI voice agents

1. 1

   Connect your SIP trunk

   Your carrier’s credentials. The password is stored encrypted and is never returned by the API again, including to you.

   POST /v1/sip-trunks

   $ curl https://api.voice.wixzel.com/v1/sip-trunks \
       -H "Authorization: Bearer $WIXZEL_API_KEY" \
       -d '{
         "name": "My carrier",
         "host": "sip.carrier.example",
         "username": "acct123",
         "password": "…"
       }'

2. 2

   Register a number on it

   Give the number an inbound_agent_id later and calls to it are answered automatically.

   POST /v1/phone-numbers

   $ curl https://api.voice.wixzel.com/v1/phone-numbers \
       -H "Authorization: Bearer $WIXZEL_API_KEY" \
       -d '{
         "phone_number": "+14155550100",
         "sip_trunk_id": "st_01HXYZ"
       }'

3. 3

   Create an agent

   Name the models you want and we wire them together, or hand the whole turn to one realtime model. All three stages are required: defaulting a missing one would bill you for a model you never chose.

   POST /v1/agents

   $ curl https://api.voice.wixzel.com/v1/agents \
       -H "Authorization: Bearer $WIXZEL_API_KEY" \
       -d '{
         "name": "Support",
         "system_prompt": "You are a concise support agent.",
         "opening_message": "Hi, how can I help?",
         "voice": {
           "stt": { "model": "deepgram/nova-3" },
           "llm": { "model": "openrouter/gpt-4o-mini" },
           "tts": { "model": "elevenlabs/eleven_turbo_v2_5" }
         }
       }'

     // or hand the whole turn to one model
     "voice": {
       "realtime": {
         "model": "google/gemini-live",
         "voice": "Charon"
       }
     }

4. 4

   Place a call

   Idempotency-Key is required here. A timeout tells you nothing about whether the call was placed; the key makes retrying safe instead of dialling twice.

   POST /v1/calls

   $ curl https://api.voice.wixzel.com/v1/calls \
       -H "Authorization: Bearer $WIXZEL_API_KEY" \
       -H "Idempotency-Key: $(uuidgen)" \
       -d '{
         "to": "+14155551234",
         "agent_id": "ag_01HXYZ"
       }'

Then GET /v1/usage/events?session_id=… explains every micro of what it cost. Read the quickstart