Linden by Speechmatics
Agent STT (also marketed as Speech-to-text for AI voice agents) is a speech-to-text API from Speechmatics built specifically for real-time conversational AI voice agents. It runs on a model Speechmatics describes as purpose-built for voice agents, and is designed to accurately capture both what was said and who said it within roughly 350 milliseconds of end-to-end latency. The service supports speaker diarization (speaker identification), making it possible for an agent to distinguish between speakers on a call in real time.
- Category
- APIs
- Pricing
- Unknown
Problem solved
Real-time voice agents need transcription that is fast enough to feel conversational and smart enough to attribute speech to the right speaker. Traditional batch or high-latency ASR adds perceptible delay and often loses speaker context, which breaks turn-taking in live calls. Agent STT addresses this by providing a streaming speech-to-text API with approximately 350ms latency, built-in speaker identification, and broad language coverage, so developers can plug low-latency, speaker-aware transcription into voice agent frameworks instead of building or tuning ASR infrastructure themselves.
Use cases
- Powering real-time speech recognition inside AI voice agents and phone bots
- Adding speaker diarization so agents know which participant said what on a call
- Live captioning and real-time subtitling for broadcasts and streams
- Transcribing contact-center and customer-support conversations in real time
- Building multilingual voice interfaces across 55+ languages
- Integrating low-latency STT into agent frameworks such as LiveKit or Pipecat
- Media monitoring and content indexing workflows that need speaker attribution
Audience
- Developers
- ML Engineers
- Product Managers
- Enterprise
- Startups
Pros
- Low ~350ms latency tuned for conversational voice agents
- Built-in speaker diarization/speaker identification
- Coverage of 55+ languages
- Accessible via direct API or popular agent frameworks (LiveKit, Pipecat)
- Transparent usage pricing starting at $0.30/hour with $100 free credit
Cons
- Proprietary, usage-based commercial API rather than open source
- No public GitHub repository or self-hosting option for the hosted service
- Pricing and quotas beyond the entry tier require contacting sales or checking the pricing page
- Exact model architecture and benchmarks are only partially disclosed publicly
- Latency and accuracy may vary by language, audio quality, and network conditions
Official website: https://www.speechmatics.com/voice-agents
Canonical LambdaBase page: https://www.lambdabase.com/tools/linden-by-speechmatics