Create Chat (OpenAI Compatible)

Request

This endpoint expects an object.

inputstring or list of objectsRequired

This is the input text for the chat. Can be a string or an array of chat messages. This field is REQUIRED for chat creation.

assistantIdstringOptional

This is the assistant that will be used for the chat. To use an existing assistant, use assistantId instead.

assistantobjectOptional

This is the assistant that will be used for the chat. To use an existing assistant, use assistantId instead.

namestringOptional<=40 characters

This is the name of the chat. This is just for your own reference.

sessionIdstringOptional

This is the ID of the session that will be used for the chat. Mutually exclusive with previousChatId.

streambooleanOptionalDefaults to true

Whether to stream the response or not.

previousChatIdstringOptional

This is the ID of the chat that will be used as context for the new chat. The messages from the previous chat will be used as context. Mutually exclusive with sessionId.

Response

OpenAI Responses API format - either non-streaming or streaming

ResponseObjectobject

ResponseTextDeltaEventobject

ResponseTextDoneEventobject

ResponseCompletedEventobject

ResponseErrorEventobject

1	curl -X POST https://api.vapi.ai/chat/responses \
2	-H "Authorization: Bearer <token>" \
3	-H "Content-Type: application/json" \
4	-d '{
5	"input": "Hello, how can you help me?"
6	}'

1	{
2	"id": "foo",
3	"object": "response",
4	"created_at": 42,
5	"status": "completed",
6	"error": "foo",
7	"output": [
8	{
9	"id": "foo",
10	"content": [
11	{
12	"annotations": [
13	{}
14	],
15	"text": "foo",
16	"type": "output_text"
17	}
18	],
19	"role": "assistant",
20	"status": "in_progress",
21	"type": "message"
22	}
23	]
24	}

Headers

Request

Response