Perform chat completion inference Added in 8.18.0

POST /_inference/chat_completion/{inference_id}/_stream
Api key auth

The chat completion inference API enables real-time responses for chat completion tasks by delivering answers incrementally, reducing response times during computation. It only works with the chat_completion task type for openai and elastic inference services.

IMPORTANT: The inference APIs enable you to use certain services, such as built-in machine learning models (ELSER, E5), models uploaded through Eland, Cohere, OpenAI, Azure, Google AI Studio, Google Vertex AI, Anthropic, Watsonx.ai, or Hugging Face. For built-in models and models uploaded through Eland, the inference APIs offer an alternative way to use and manage trained models. However, if you do not plan to use the inference APIs to use these models or if you want to use non-NLP models, use the machine learning trained model APIs.

NOTE: The chat_completion task type is only available within the _stream API and only supports streaming. The Chat completion inference API and the Stream inference API differ in their response structure and capabilities. The Chat completion inference API provides more comprehensive customization options through more fields and function calling support. If you use the openai service or the elastic service, use the Chat completion inference API.

Path parameters

Query parameters

  • timeout string

    Specifies the amount of time to wait for the inference request to complete.

application/json

Body Required

  • messages array[object] Required

    A list of objects representing the conversation. Requests should generally only add new messages from the user (role user). The other message roles (assistant, system, or tool) should generally only be copied from the response to a previous completion request, such that the messages array is built up throughout a conversation.

    Hide messages attributes Show messages attributes object
  • model string

    The ID of the model to use.

  • max_completion_tokens number

    The upper bound limit for the number of tokens that can be generated for a completion request.

  • stop array[string]

    A sequence of strings to control when the model should stop generating additional tokens.

  • temperature number

    The sampling temperature to use.

  • tool_choice string | object

    One of:
    CompletionToolType string CompletionToolChoice object
  • tools array[object]

    A list of tools that the model can call.

    Hide tools attributes Show tools attributes object
    • type string Required

      The type of tool.

    • function object Required
      Hide function attributes Show function attributes object
      • description string

        A description of what the function does. This is used by the model to choose when and how to call the function.

      • name string Required

        The name of the function.

      • parameters object

        The parameters the functional accepts. This should be formatted as a JSON object.

      • strict boolean

        Whether to enable schema adherence when generating the function call.

  • top_p number

    Nucleus sampling, an alternative to sampling with temperature.

Responses

POST /_inference/chat_completion/{inference_id}/_stream 
curl \
 --request POST 'http://api.example.com/_inference/chat_completion/{inference_id}/_stream' \
 --header "Authorization: $API_KEY" \
 --header "Content-Type: application/json" \
 --data '"{\n  \"model\": \"gpt-4o\",\n  \"messages\": [\n      {\n          \"role\": \"user\",\n          \"content\": \"What is Elastic?\"\n      }\n  ]\n}"'
Request examples
Run `POST _inference/chat_completion/openai-completion/_stream` to perform a chat completion on the example question with streaming. 
{
  "model": "gpt-4o",
  "messages": [
      {
          "role": "user",
          "content": "What is Elastic?"
      }
  ]
}
Run `POST POST _inference/chat_completion/openai-completion/_stream` to perform a chat completion using an Assistant message with `tool_calls`. 
{
  "messages": [
      {
          "role": "assistant",
          "content": "Let's find out what the weather is",
          "tool_calls": [ 
              {
                  "id": "call_KcAjWtAww20AihPHphUh46Gd",
                  "type": "function",
                  "function": {
                      "name": "get_current_weather",
                      "arguments": "{\"location\":\"Boston, MA\"}"
                  }
              }
          ]
      },
      { 
          "role": "tool",
          "content": "The weather is cold",
          "tool_call_id": "call_KcAjWtAww20AihPHphUh46Gd"
      }
  ]
}
Run `POST POST _inference/chat_completion/openai-completion/_stream` to perform a chat completion using a User message with `tools` and `tool_choice`. 
{
  "messages": [
      {
          "role": "user",
          "content": [
              {
                  "type": "text",
                  "text": "What's the price of a scarf?"
              }
          ]
      }
  ],
  "tools": [
      {
          "type": "function",
          "function": {
              "name": "get_current_price",
              "description": "Get the current price of a item",
              "parameters": {
                  "type": "object",
                  "properties": {
                      "item": {
                          "id": "123"
                      }
                  }
              }
          }
      }
  ],
  "tool_choice": {
      "type": "function",
      "function": {
          "name": "get_current_price"
      }
  }
}
Response examples (200)
A successful response when performing a chat completion task using a User message with `tools` and `tool_choice`. 
event: message
data: {"chat_completion":{"id":"chatcmpl-Ae0TWsy2VPnSfBbv5UztnSdYUMFP3","choices":[{"delta":{"content":"","role":"assistant"},"index":0}],"model":"gpt-4o-2024-08-06","object":"chat.completion.chunk"}}

event: message
data: {"chat_completion":{"id":"chatcmpl-Ae0TWsy2VPnSfBbv5UztnSdYUMFP3","choices":[{"delta":{"content":Elastic"},"index":0}],"model":"gpt-4o-2024-08-06","object":"chat.completion.chunk"}}

event: message
data: {"chat_completion":{"id":"chatcmpl-Ae0TWsy2VPnSfBbv5UztnSdYUMFP3","choices":[{"delta":{"content":" is"},"index":0}],"model":"gpt-4o-2024-08-06","object":"chat.completion.chunk"}}

(...)

event: message
data: {"chat_completion":{"id":"chatcmpl-Ae0TWsy2VPnSfBbv5UztnSdYUMFP3","choices":[],"model":"gpt-4o-2024-08-06","object":"chat.completion.chunk","usage":{"completion_tokens":28,"prompt_tokens":16,"total_tokens":44}}} 

event: message
data: [DONE]