A Hindi and Malayalam phone agent on Wixzel Voice's sarvam engine

What do you need before you start?

• A Wixzel Voice API key with credit, exported as WIXZEL_API_KEY.
• A SIP trunk with a number on it. For Indian numbers, a carrier such as Exotel or Vobiz, with KYC and any DLT registration finished: an account that has not finished them can hold a balance and still have every outbound call cleared.
• curl, jq and uuidgen.

How do you build this on Wixzel Voice, step by step?

1. 01Check the languages and voices the engine serves

   Ask the API rather than hardcoding either list:

   shellCopy

   curl https://api.voice.wixzel.com/v1/engines/sarvam/languages \
     -H "Authorization: Bearer $WIXZEL_API_KEY"
   
   curl https://api.voice.wixzel.com/v1/engines/sarvam/voices \
     -H "Authorization: Bearer $WIXZEL_API_KEY"

   The languages endpoint returns 11 codes today: en-IN, hi-IN, bn-IN, gu-IN, kn-IN, ml-IN, mr-IN, od-IN, pa-IN, ta-IN, te-IN. Hindi is hi-IN and Malayalam is ml-IN. The voices are Bulbul v3 speaker names, such as priya, kavya and shubh; Sarvam publishes the names and nothing else, so audition a voice before you choose it.

2. 02Create the Hindi agent

   Three settings carry the language. voice.stt.language pins recognition and speech to Hindi; the agent's language tells the model to reply in it; and the prompt and opening line are written the way the agent should sound. All three stages are Sarvam models, because the speech-to-text provider selects the pipeline and the other two must come from the same family.

   shellCopy

   curl https://api.voice.wixzel.com/v1/agents \
     -H "Authorization: Bearer $WIXZEL_API_KEY" \
     -H "Content-Type: application/json" \
     -d '{
       "name": "Hindi reception",
       "language": "hi-IN",
       "system_prompt": "You answer the phone for Sharma Dental Clinic, in Hindi. Speak the everyday Hindi callers use, English words included. Keep replies to one or two short sentences.",
       "opening_message": "नमस्ते, शर्मा डेंटल क्लिनिक में आपका स्वागत है। बताइए, मैं आपकी क्या मदद करूँ?",
       "voice": {
         "stt": { "model": "sarvam/saaras-v3-realtime", "language": "hi-IN" },
         "llm": { "model": "sarvam/sarvam-105b" },
         "tts": { "model": "sarvam/bulbul-v3", "voice": "priya" }
       }
     }'

   Keep the id from the response as HINDI_AGENT_ID. A language or voice the engine does not serve is refused when the agent is created, with the valid ones listed in the error.

3. 03Create the Malayalam agent

   The same shape, with ml-IN in both places and a Malayalam opening line:

   shellCopy

   curl https://api.voice.wixzel.com/v1/agents \
     -H "Authorization: Bearer $WIXZEL_API_KEY" \
     -H "Content-Type: application/json" \
     -d '{
       "name": "Malayalam reception",
       "language": "ml-IN",
       "system_prompt": "You answer the phone for a dental clinic in Kochi, in Malayalam. Speak the everyday Malayalam callers use, English words included. Keep replies to one or two short sentences.",
       "opening_message": "നമസ്കാരം, കൊച്ചി ഡെന്റൽ ക്ലിനിക്കിലേക്ക് സ്വാഗതം. ഞാൻ എങ്ങനെ സഹായിക്കാം?",
       "voice": {
         "stt": { "model": "sarvam/saaras-v3-realtime", "language": "ml-IN" },
         "llm": { "model": "sarvam/sarvam-105b" },
         "tts": { "model": "sarvam/bulbul-v3", "voice": "kavya" }
       }
     }'

   Keep this id as MALAYALAM_AGENT_ID. One agent speaks one language: the sarvam engine has no automatic detection mode, so serving both groups of callers means one number per language on the way in, and choosing the agent per call on the way out.

4. 04Route calls in, or place one out

   Give a number the Hindi agent for inbound calls, or ring someone with the Malayalam one:

   shellCopy

   # Inbound: calls to this number reach the Hindi agent
   jq -n --arg agent "$HINDI_AGENT_ID" '{inbound_agent_id: $agent}' |
     curl -X PATCH https://api.voice.wixzel.com/v1/phone-numbers/$NUMBER_ID \
       -H "Authorization: Bearer $WIXZEL_API_KEY" \
       -H "Content-Type: application/json" \
       -d @-
   
   # Outbound: the Malayalam agent rings $TO (E.164, for example +91 and ten digits)
   jq -n --arg to "$TO" --arg agent "$MALAYALAM_AGENT_ID" --arg from "$NUMBER_ID" \
     '{to: $to, agent_id: $agent, from_number_id: $from}' |
     curl https://api.voice.wixzel.com/v1/calls \
       -H "Authorization: Bearer $WIXZEL_API_KEY" \
       -H "Idempotency-Key: $(uuidgen)" \
       -H "Content-Type: application/json" \
       -d @-

   Idempotency-Key is required on POST /v1/calls: a retry with the same key returns the original call instead of dialling twice.

5. 05Test with the way your callers really talk

   Most callers mix English into Hindi or Malayalam: dates, numbers, brand names, words like "appointment" and "cancel". Sarvam's models cope with code-mixed speech such as Hinglish, within what the models handle, so write the prompt to allow it rather than forbid it.

   What the agent cannot do is follow a caller who switches wholly to another Indian language, because recognition is pinned to voice.stt.language when the call starts. Place a few calls with real phrasing before you route live traffic, and read what was heard in the transcript from GET /v1/calls/{id}.

What does this build cost on Wixzel Voice?

Which Wixzel Voice limits apply to this build?

• One language per agent. The sarvam engine has no automatic language detection, so a caller who switches wholly to another language is not followed.
• Sarvam processes speech and text in India during the call. The call log, the transcript and any recording are stored on servers in Finland.
• Bulbul voices come as names only, with no gender or accent descriptions. Auditioning one means a test call, which rings a real phone and spends credit.
• Indian carriers gate outbound calling behind KYC and often DLT registration. A call your carrier clears for that reason fails at the carrier, and nothing on the platform side can fix it.
• Five calls can be live at once per account by default, raised on request.