How to Create AI Judge Metrics You Can Trust
How to use human review in Coval to calibrate your LLM-as-a-judge metrics: label conversations, check agreement, read disagreements, fix the prompt, and re-test.
Blog
Coval's observations on developing and shipping AI voice agents
More reading
TTS Latency 2026: The Production Speed Metric for Voice AI
Latency is what separates a natural conversation from a phone tree. TTFA, Coval's streaming methodology, and July 2026 results. Read the benchmark.
Word Error Rate 2026: The Production Accuracy Filter for STT
How to use Word Error Rate as an accuracy filter, interpret Coval's July 2026 STT snapshot, and choose among models that clear your production threshold.
Voice AI Benchmark: TTS and STT Results via API
How Coval continuously benchmarks 55+ TTS and STT models for latency and accuracy under production-realistic conditions.
Voice Agent Vendor Testing: How to Run a Bake-Off
How to run a voice AI vendor bake-off that picks the vendor your callers actually experience: the failure modes, the four shapes, and a defensible seven-step method.
Best STT Providers 2026: Independent Benchmarks & How to Choose
Best speech-to-text providers in 2026: Deepgram, AssemblyAI, Whisper, ElevenLabs Scribe, MAI-Transcribe. WER, latency, pricing. See the guide.
Best TTS Providers 2026: Why Vendor Benchmarks Lie
Best TTS providers in 2026: ElevenLabs v3, Cartesia Sonic 3, OpenAI Realtime, Deepgram Aura-2, Vapi Voices. Latency, pricing, voice cloning. See the guide.
Vapi Review 2026: Composer, Evals & Vapi Voices
Vapi review for 2026: Composer builder, Vapi Voices, Monitoring, Evals, Simulations, GPT-5 + Realtime, and post-Series B pricing. Read the guide.
ElevenLabs Voice Cloning Review 2026: v3, Scribe & Agents
ElevenLabs voice cloning in 2026: IVC vs PVC requirements, Eleven v3 vs Flash v2.5, Scribe v2 STT, ElevenAgents, and the May pricing reset. Read the guide.
CI/CD for Voice AI Agents: The 2026 Pipeline Guide
Voice agents are software. CI/CD pipelines with automated eval gates are how mature teams ship them. Patterns, tools, and pipeline design.