Chat Completion response object

Single Chat Completion response returned by the model.

Attributes

• id string
  Chat response ID.
• object string
  Response object type, always chat.completion.
• model string
  Model name.
• created timestamp
  Unix timestamp (seconds) when the response was generated.
• choices object array
  List of response choices.
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  • finish_reason string
    Why generation stopped.
  • index int
    Choice index.
  • message object
    Actual message content.

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  • role string
    Message role, always assistant.
  • content string
    Message text.
  • reasoning string
    Reasoning content (only for step reasoning models).
  • tool_calls object array optional
    Toolcall results.

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  • id string
    Function call ID generated by the model; unique in context.
  • type string
    Toolcall type, always function.
  • function object
    Function payload.

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  • name string
    Function name, typically one from the tools list of the previous turn.
  • arguments string
    Function arguments as a JSON string.
• usage object
  Token usage statistics.
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  • prompt_tokens int
    Prompt tokens used.
  • cached_tokens int optional
    Prompt tokens served from cache.
  • completion_tokens int
    Completion tokens generated.
  • total_tokens int
    Total tokens.

Example

{
	"id": "b7b56af0-52a6-483f-a589-948182676a1b",
	"object": "chat.completion",
	"created": 1709893411,
	"model": "step-3.5-flash",
	"choices": [
		{
			"index": 0,
			"message": {
				"role": "assistant",
				"content": "Hello! StepFun specializes in artificial intelligence and provides AI solutions across NLP, computer vision, and machine learning to help customers improve efficiency and create value across industries."
			},
			"finish_reason": "stop"
		}
	],
	"usage": { "prompt_tokens": 83, "completion_tokens": 176, "total_tokens": 259 }
}