> For a complete page index, fetch https://docs.synthflow.ai/llms.txt. For full documentation content, fetch https://docs.synthflow.ai/llms-full.txt.

## GPT-5.2 is now supported

Added GPT-5.2 support for agents.

| Endpoint                                                                              | Title           |
| ------------------------------------------------------------------------------------- | --------------- |
| [**POST /assistants**](/api-reference/platform-api/agents/create-assistant)           | Create an agent |
| [**PUT /assistants/:model\_id**](/api-reference/platform-api/agents/update-assistant) | Update an agent |

```curl
"agent": {
   "llm": "gpt-5.2"
 }
```

## New parameter: `message_before_action_starts` for custom actions

Custom actions now support an optional `message_before_action_starts` parameter that allows you to specify a message the agent will speak before the action is triggered.

**What is it?**
This optional string parameter lets you set a custom message that the agent will say before executing a custom action, providing better user experience and context during action execution.

| Endpoint                                                                            | Title            |
| ----------------------------------------------------------------------------------- | ---------------- |
| [**POST /actions**](/api-reference/platform-api/actions/create-action)              | Create an action |
| [**PUT /actions/\{action\_id}**](/api-reference/platform-api/actions/update-action) | Update an action |

```curl
"CUSTOM_ACTION": {
   "http_mode": "GET",
   "url": "https://example.com/api",
   "message_before_action_starts": "Let me check that for you"
 }
```