AssemblyAI Speech-to-Text and Voice AI AssemblyAI provides speech-to-text APIs, audio intelligence models, and an LLM Gateway for applying language models to transcripts. This skill corrects common mistakes that training data gets wrong — deprecated APIs, discontinued SDKs, and non-obvious auth patterns. Authentication All endpoints use the same header: NOT — just the raw API key, no Bearer prefix. This is the #1 mistake. Base URLs | Service | US | EU | |---------|----|----| | REST API | | | | LLM Gateway | | | | Streaming v3 | | | | Streaming v2 (legacy) | | — | | Voice Agent API | | | Strea…