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# Update prompt description

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

Updates the description of a **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/update-prompt-description

## 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.
- `version` (integer, required) — Version number for a Prompt. Prompts, Configs, Custom Voices, and Tools are versioned. This versioning system supports iterative development, allowing you to progressively refine prompts and revert to previous versions if needed. Version numbers are integer values representing different iterations of the Prompt. Each update to the Prompt increments its version number.

### Body (application/json)

This endpoint expects a patched_prompt_version_description.

- `version_description` (string, optional, nullable) — An optional description of the Prompt version.

## Response

### 200

Success

- `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
{
  "version_description": "This is an updated version_description."
}
```

**Response**

```json
{
  "created_on": 1722633247488,
  "id": "af699d45-2985-42cc-91b9-af9e5da3bac5",
  "modified_on": 1722634770585,
  "name": "string",
  "text": "<role>You are 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_description."
}
```