Chat Completion streaming chunk

Streaming chunk returned by the Chat Completion API.

Attributes

• id string
  Generated chat response ID.
• object string
  Response object type, always chat.completion.chunk.
• created timestamp
  Unix timestamp (seconds) when the chunk was generated.
• model string
  Model name.
• choices object array
  List of streamed response alternatives. Each choice object:
  Expand/Collapse

  • finish_reason string
    Why generation stopped.
  • index int
    Choice index.
  • delta object
    Incremental response chunk.

  Expand/Collapse

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

  Expand/Collapse

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

  Expand/Collapse

  • name string
    Function name, usually the name provided in the previous turn’s tools list.
  • arguments string
    Function arguments as a JSON string.
• usage object
  Token usage statistics.
  Expand/Collapse

  • 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

data: {"id":"d7ae7c4a-1524-4fe5-9d58-e4d59b89d8f0","object":"chat.completion.chunk","created":1709899323,"model":"step-3.5-flash","choices":[{"index":0,"delta":{"role":"","content":"Hello"},"finish_reason":""}],"usage":{"prompt_tokens":83,"completion_tokens":1,"total_tokens":84}}

...

data: {"id":"d7ae7c4a-1524-4fe5-9d58-e4d59b89d8f0","object":"chat.completion.chunk","created":1709899323,"model":"step-3.5-flash","choices":[{"index":0,"delta":{"role":"","content":"value"},"finish_reason":""}],"usage":{"prompt_tokens":83,"completion_tokens":148,"total_tokens":231}}

data: {"id":"d7ae7c4a-1524-4fe5-9d58-e4d59b89d8f0","object":"chat.completion.chunk","created":1709899323,"model":"step-3.5-flash","choices":[{"index":0,"delta":{"role":"","content":""},"finish_reason":"stop"}],"usage":{"prompt_tokens":83,"completion_tokens":150,"total_tokens":233}}

data: [DONE]