> This page is for Voice APIs.

> For clean Markdown of any page, append .md to the page URL.
> For a complete documentation index, see https://dev.hume.ai/llms.txt.
> For AI client integration (Claude Code, Cursor, etc.), connect to the MCP server at https://dev.hume.ai/_mcp/server.

# Create prompt version

POST https://api.hume.ai/v0/evi/prompts/{id}
Content-Type: application/json

Updates a **Prompt** by creating a new version of the **Prompt**.

See our [prompting guide](/docs/speech-to-speech-evi/guides/phone-calling) for tips on crafting your system prompt.

Reference: https://dev.hume.ai/voice/reference/speech-to-speech-evi/prompts/create-prompt-version

## Authentication

- `X-Hume-Api-Key` header (required) — API Key authentication via header

## Request

### Path parameters

- `id` (string, required) — Identifier for a Prompt. Formatted as a UUID.

### Body (application/json)

This endpoint expects a posted_prompt_version.

- `text` (string, required) — Instructions used to shape EVI's behavior, responses, and style. You can use the Prompt to define a specific goal or role for EVI, specifying how it should act or what it should focus on during the conversation. For example, EVI can be instructed to act as a customer support representative, a fitness coach, or a travel advisor, each with its own set of behaviors and response styles. For help writing a system prompt, see our [Prompting Guide](/docs/speech-to-speech-evi/guides/prompting).
- `prompt_expansion` (prompt_expansion_spec, optional) — Configuration for prompt expansion behavior.
- `version_description` (string, optional, nullable) — An optional description of the Prompt version.

## Response

### 201

Created

- `created_on` (long, required) — Time at which the Prompt was created. Measured in seconds since the Unix epoch.
- `id` (string, required) — Identifier for a Prompt. Formatted as a UUID.
- `modified_on` (long, required) — Time at which the Prompt was last modified. Measured in seconds since the Unix epoch.
- `name` (string, required) — Name applied to all versions of a particular Prompt.
- `text` (string, required) — Instructions used to shape EVI's behavior, responses, and style. You can use the Prompt to define a specific goal or role for EVI, specifying how it should act or what it should focus on during the conversation. For example, EVI can be instructed to act as a customer support representative, a fitness coach, or a travel advisor, each with its own set of behaviors and response styles. For help writing a system prompt, see our [Prompting Guide](/docs/speech-to-speech-evi/guides/prompting).
- `version` (integer, required) — Version number for a Prompt. Version numbers should be integers. The combination of configId and version number is unique.
- `version_type` (string, required) — Indicates whether this prompt is using a fixed version number or auto-updating to the latest version. Values from the VersionType enum.
- `prompt_expansion` (prompt_expansion_spec, optional) — Configuration for prompt expansion behavior.
- `version_description` (string, optional, nullable) — An optional description of the Prompt version.

## Types

### prompt_expansion_spec

Configuration for prompt expansion behavior.

- `enabled` (boolean, optional) — Boolean indicating whether prompt expansion is enabled. Defaults to `true`. When set to `false`, no additional instructions are appended to the system prompt, giving full control over the prompt content. Only applicable when using an external supplemental language model.

## Examples

**Request**

```json
{
  "text": "<role>You are an updated version of an AI weather assistant providing users with accurate and up-to-date weather information. Respond to user queries concisely and clearly. Use simple language and avoid technical jargon. Provide temperature, precipitation, wind conditions, and any weather alerts. Include helpful tips if severe weather is expected.</role>",
  "version_description": "This is an updated version of the Weather Assistant Prompt."
}
```

**Response**

```json
{
  "created_on": 1722633247488,
  "id": "af699d45-2985-42cc-91b9-af9e5da3bac5",
  "modified_on": 1722635140150,
  "name": "Weather Assistant Prompt",
  "text": "<role>You are an updated version of an AI weather assistant providing users with accurate and up-to-date weather information. Respond to user queries concisely and clearly. Use simple language and avoid technical jargon. Provide temperature, precipitation, wind conditions, and any weather alerts. Include helpful tips if severe weather is expected.</role>",
  "version": 1,
  "version_type": "FIXED",
  "version_description": "This is an updated version of the Weather Assistant Prompt."
}
```