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# Create tool version

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

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

Refer to our [tool use](/docs/speech-to-speech-evi/features/tool-use#function-calling) guide for comprehensive instructions on defining and integrating tools into EVI.

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

## Authentication

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

## Request

### Path parameters

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

### Body (application/json)

This endpoint expects a posted_user_defined_tool_version.

- `parameters` (string, required) — Stringified JSON defining the parameters used by this version of the Tool. These parameters define the inputs needed for the Tool's execution, including the expected data type and description for each input field. Structured as a stringified JSON schema, this format ensures the Tool receives data in the expected format.
- `description` (string, optional, nullable) — An optional description of what the Tool does, used by the supplemental LLM to choose when and how to call the function.
- `fallback_content` (string, optional, nullable) — Optional text passed to the supplemental LLM in place of the tool call result. The LLM then uses this text to generate a response back to the user, ensuring continuity in the conversation if the Tool errors.
- `version_description` (string, optional, nullable) — An optional description of the Tool version.

## Response

### 201

Created

- `created_on` (long, required) — The timestamp when the first version of this tool was created.
- `id` (string, required) — Identifier for a Tool. Formatted as a UUID.
- `modified_on` (long, required) — The timestamp when this version of the tool was created.
- `name` (string, required) — Name of the built-in tool to use. Hume supports the following built-in tools: - **web_search:** enables EVI to search the web for up-to-date information when applicable. - **hang_up:** closes the WebSocket connection when appropriate (e.g., after detecting a farewell in the conversation). For more information, see our guide on [using built-in tools](/docs/speech-to-speech-evi/features/tool-use#using-built-in-tools).
- `parameters` (string, required) — Stringified JSON defining the parameters used by this version of the Tool. These parameters define the inputs needed for the Tool's execution, including the expected data type and description for each input field. Structured as a stringified JSON schema, this format ensures the Tool receives data in the expected format.
- `tool_type` (enum, required)
  - Allowed values: `BUILTIN`, `FUNCTION`
- `version` (integer, required) — Version number for a Tool. Version numbers should be integers. The combination of configId and version number is unique.
- `version_type` (enum, required)
  - Allowed values: `FIXED`, `LATEST`
- `description` (string, optional, nullable) — An optional description of what the Tool does, used by the supplemental LLM to choose when and how to call the function.
- `fallback_content` (string, optional, nullable) — Optional text passed to the supplemental LLM in place of the tool call result. The LLM then uses this text to generate a response back to the user, ensuring continuity in the conversation if the Tool errors.
- `version_description` (string, optional, nullable) — An optional description of the Tool version.

## Examples

**Request**

```json
{
  "parameters": "{ \"type\": \"object\", \"properties\": { \"location\": { \"type\": \"string\", \"description\": \"The city and state, e.g. San Francisco, CA\" }, \"format\": { \"type\": \"string\", \"enum\": [\"celsius\", \"fahrenheit\", \"kelvin\"], \"description\": \"The temperature unit to use. Infer this from the users location.\" } }, \"required\": [\"location\", \"format\"] }",
  "description": "This tool is for getting the current weather.",
  "fallback_content": "Unable to fetch current weather.",
  "version_description": "Fetches current weather and uses celsius, fahrenheit, or kelvin based on location of user."
}
```

**Response**

```json
{
  "created_on": 1715277014228,
  "id": "00183a3f-79ba-413d-9f3b-609864268bea",
  "modified_on": 1715277602313,
  "name": "get_current_weather",
  "parameters": "{ \"type\": \"object\", \"properties\": { \"location\": { \"type\": \"string\", \"description\": \"The city and state, e.g. San Francisco, CA\" }, \"format\": { \"type\": \"string\", \"enum\": [\"celsius\", \"fahrenheit\", \"kelvin\"], \"description\": \"The temperature unit to use. Infer this from the users location.\" } }, \"required\": [\"location\", \"format\"] }",
  "tool_type": "FUNCTION",
  "version": 1,
  "version_type": "FIXED",
  "description": "This tool is for getting the current weather.",
  "fallback_content": "Unable to fetch current weather.",
  "version_description": "Fetches current weather and uses celsius, fahrenheit, or kelvin based on location of user."
}
```