Developer guides
Learn to build voice agents.
How to build with our speech and agent APIs: Hindi text to speech, speech to text, the Realtime API, phone calls from code and bulk campaigns.
- 21guides in 5 topics, from a first call to the GPUs
- 71references cited and linked
Voice infrastructure
These notes measure the stack under a voice agent.
The infrastructure notes on Gemma, FP4, vLLM and context management are here too, with their data.
- Making Gemma 4 26B A4B fast enough for a voice conversation Published 17 September 2026
A Gemma voice-serving case study: 1,520 measured requests, concurrency trade-offs, connection reuse and a downloadable analysis kit.
- How FP4 can help voice inference—and what it cannot promise Published 17 September 2026
Understand NVFP4 with Gemma 4 26B A4B: weight memory, hardware kernels, FP8 KV cache and the experiment needed to prove a latency improvement.
- Tune vLLM for voice latency, not just tokens per second Published 17 September 2026
Use our archived concurrency sweep to understand vLLM batching, tail latency, prefill budgets, warmup and goodput for voice workloads.
- Manage voice-agent context before buying more inference capacity Published 17 September 2026
Measured shared-prefix results, KV capacity arithmetic and a practical context budget for voice agents using Gemma and vLLM.
Agent design
Design an agent that keeps the call on track.
Prompts, flows and the tests that tell you a rewrite helped.
- Prompt-based or node-based voice agent: how to choose Updated 16 October 2026
One prompt or a graph of nodes? Choose by branching, risk and recovery: how our node-based agents run, an appointment example and test cases.
- How to fix an overloaded voice-agent prompt Updated 16 October 2026
Fix contradicting instructions, move state and permissions into code, give each turn only what it needs, read the agent's logs and test corrections.
Start building
Start here to place your first call from code.
Keys, a first call, a webhook and a campaign, with the requests written out.
- Voice AI APIs for developers building in India Updated 16 October 2026
Which Frequency API to start with: phone agents, the Realtime API, Fourier TTS or transcription. What each one does, and how a call works.
- Integrated voice API or build your own stack? Updated 16 October 2026
A hosted voice-agent API, a speech-to-speech Realtime API, or a stack you build from ASR, LLM and TTS: control, latency, cost and who runs it.
- Voice AI API pricing: minutes, characters and commitments Updated 16 October 2026
How we bill voice agents, Realtime sessions, TTS and transcription: rates, 10-second blocks, what's free, commitments, and worked monthly estimates.
- Make an AI phone call from Python with the Mirai API Published 16 October 2026
Place a real AI phone call in Hindi, Tamil or Telugu from Python, then read the transcript off a signed webhook. Three requests, with httpx and Flask.
- Run bulk AI calls from a CSV with a Mirai campaign Published 16 October 2026
Upload a CSV this afternoon and an AI agent calls every row in Hindi, Tamil, Telugu and more, inside your hours, with retries and a result per contact.
Speech APIs
Turn text into speech, and speech into text.
Hindi text to speech, speech to text and the Realtime API, with prices compared.
- Choosing a Hindi and Hinglish text-to-speech API Updated 16 October 2026
How to judge Fourier TTS on Hindi and Hinglish: script, code-switching, numbers, the four voices, streaming for phone lines and a starter test set.
- Use Fourier TTS with an OpenAI-compatible speech client Updated 16 October 2026
On OpenAI's speech API? Change the base URL, model and voice, and your code speaks Hindi, Tamil, Telugu and more with Fourier TTS. Formats and streaming.
- Hindi and Hinglish TTS in Pipecat with pipecat-mirai Published 16 October 2026
Swap one service and your Pipecat bot speaks Hindi and Hinglish. pipecat-mirai 0.5.1: install, pipeline, an 8 kHz phone setup, Realtime and fixes.
- Hindi speech-to-text API: transcribe calls with Mira Published 16 October 2026
Send a Hindi or Hinglish call recording and get back who said what, with timestamps. The /v2/transcriptions request, polling, speakers and ₹18 an hour.
- Hindi text-to-speech APIs compared: prices and features, October 2026 Published 16 October 2026
Published prices and Hindi support for Fourier TTS, Sarvam Bulbul, ElevenLabs, Google, Azure, Amazon Polly, OpenAI and Cartesia, each sourced and dated.
- Hindi speech-to-text APIs compared: prices and features, October 2026 Published 16 October 2026
Published prices and Hindi support for Frequency, Sarvam, ElevenLabs, Deepgram, Google, Azure, Amazon Transcribe and OpenAI, sourced and dated.
- Realtime speech-to-speech API for Hindi voice agents Published 16 October 2026
Send a caller's audio over one WebSocket and get the reply spoken in Hindi, English, Gujarati, Tamil or Telugu. OpenAI Realtime protocol, barge-in, tools.
- Voice AI infrastructure in India: TTS, STT, LLM and agent APIs Published 16 October 2026
Who sells TTS, STT, LLM and agent APIs in India: published prices, Hindi support and where the audio is processed, read on 16 October 2026.
Production engineering
Keep your calls healthy once they are live.
Webhooks you can trust, and latency you can measure.
- Connect voice-agent webhooks to your application Updated 16 October 2026
Hear about every call the moment it changes. Verify the signature on the raw body, store before you answer, ignore retried duplicates, order by status.
- How to measure latency in a voice AI application Updated 16 October 2026
Split the delay a caller hears into turn detection, the model, TTS first byte, the network and playback, and read what Mira's request log reports.