> ## Documentation Index
> Fetch the complete documentation index at: https://docs.zeroruntime.ai/llms.txt
> Use this file to discover all available pages before exploring further.

# AssemblyAI

> Use the AssemblyAI speech-to-text plugin in a Zero Runtime pipeline. Setup and usage in Python, JavaScript, and Go.

AssemblyAI is a **speech-to-text** plugin. It transcribes the caller's audio into text for
the LLM, using AssemblyAI's universal streaming model with built-in end-of-turn detection.

## Setup

Set your AssemblyAI API key in the worker environment. Generate a key from the [AssemblyAI dashboard](https://www.assemblyai.com/dashboard/docs/your-api-key):

```bash theme={null}
export ASSEMBLYAI_API_KEY=<key>
```

<Note>
  The Python SDK requires `scipy` for audio resampling. Install it with `pip install scipy`
  if it isn't already present.
</Note>

## Usage

Import the plugin and pass it to the pipeline's `stt` slot.

<CodeGroup>
  ```python Python theme={null}
  from zrt.plugins import AssemblyAISTT

  stt = AssemblyAISTT()

  # Pipeline(stt=stt, ...)
  ```
</CodeGroup>

## Parameters

*Constructor parameters for the Python SDK (`AssemblyAISTT`). The JavaScript and Go SDKs expose equivalent options where supported, in their idiomatic form (camelCase / `STTOptions` struct).*

| Parameter                                | Type        | Default                         | Description                                                                                 |
| ---------------------------------------- | ----------- | ------------------------------- | ------------------------------------------------------------------------------------------- |
| `api_key`                                | `str`       | `None`                          | AssemblyAI API key. Falls back to the `ASSEMBLYAI_API_KEY` environment variable when unset. |
| `input_sample_rate`                      | `int`       | `48000`                         | Sample rate (Hz) of the incoming audio.                                                     |
| `output_sample_rate`                     | `int`       | `16000`                         | Sample rate (Hz) the audio is resampled to before it is sent to AssemblyAI.                 |
| `format_turns`                           | `bool`      | `True`                          | Apply capitalization and punctuation to completed turns.                                    |
| `keyterms_prompt`                        | `list[str]` | `None`                          | Words or phrases to bias recognition toward.                                                |
| `end_of_turn_confidence_threshold`       | `float`     | `0.4`                           | Confidence above which a turn is considered finished.                                       |
| `min_end_of_turn_silence_when_confident` | `int`       | `560`                           | Milliseconds of silence required to end a turn when end-of-turn confidence is high.         |
| `max_turn_silence`                       | `int`       | `2400`                          | Maximum silence (ms) allowed within a turn before it ends.                                  |
| `speech_model`                           | `str`       | `"universal-streaming-english"` | Recognition model: `"universal-streaming-english"` or `"universal-streaming-multilingual"`. |
| `language_detection`                     | `bool`      | `False`                         | Automatically detect the spoken language.                                                   |

## Import paths

| SDK        | Import                                  | Constructor                                  |
| ---------- | --------------------------------------- | -------------------------------------------- |
| Python     | `from zrt.plugins import AssemblyAISTT` | `AssemblyAISTT()`                            |
| JavaScript | `from '@zrt/js-sdk/plugins/assemblyai'` | `AssemblyAISTT()`                            |
| Go         | `.../zrt-golang-sdk/plugins/assemblyai` | `assemblyai.NewSTT(assemblyai.STTOptions{})` |

Transcribed text passes to the [LLM](/plugins/llm/google) once
[turn detection](/plugins/turn-detection/namo) decides the caller has finished speaking.