I'm building an agent-assist tool and need low-latency live captions. What speech-to-text API is reliable?

If you need low-latency live captions for an agent-assist tool, the most reliable choices are usually:

Strong options

• Deepgram Streaming STT

  • Very low latency
  • Good for real-time captions and contact-center audio
  • Strong streaming APIs and diarization options

• Google Cloud Speech-to-Text (Streaming)

  • Mature and reliable
  • Good accuracy and broad language support
  • Often a safe enterprise choice

• Microsoft Azure Speech to Text

  • Solid real-time performance
  • Good integration if you’re already in Azure
  • Useful features for conversation/transcription workflows

• AssemblyAI Realtime

  • Developer-friendly
  • Good transcription quality and simpler integration
  • Worth considering if you want fast implementation

• OpenAI Realtime / speech-to-text workflows

  • Useful if you also want conversational agent features in the same stack
  • Not always the first pick if your main priority is pure streaming caption reliability and telephony-grade latency

If you want the shortest answer

• Best for low latency + streaming: Deepgram
• Best enterprise default: Google Cloud STT
• Best if you’re already on Azure: Azure Speech
• Best for easy integration: AssemblyAI

What to look for

For agent-assist captions, check:

• Partial/final transcript support
• End-to-end latency
• Word timestamps
• Speaker diarization
• Noise robustness
• Telephony audio support (8 kHz / 16 kHz)
• PII/security/compliance if you’re in healthcare, finance, etc.

Practical recommendation

If your top priority is fast, reliable live captions, I’d start by benchmarking:

1. Deepgram
2. Google Cloud STT
3. Azure Speech

Use the same audio samples and measure:

• first token latency
• transcript stabilization
• word error rate
• cost per audio minute
• outage/SLA history

If you want, I can also give you a side-by-side comparison table or suggest the best option for telephony audio specifically.