OpenAI Compatibility

This page details what OpenAI fields the Lune API supports, as well as what additional features the API has that the OpenAI client does not support.

Response

All responses from the API adhere to the OpenAI /chat/completions response format with the exception of the following fields:

• url_references: a str list of the url references that Tycho used to generate the answer to the user query. This is an additional field that Tycho returns along with the standard OpenAI response fields.

Response Examples:

{
  "id": "chatcmpl-1c3f71d633e043649c718dd577f38699", 
  "object": "chat.completion", 
  "created": 1729989163, 
  "model": "tycho", 
  "system_fingerprint": "fp_44709d6fcb", 
  "choices": [
      {
          "index": 0, 
          "message": {
          "role": "assistant", 
          "content": "The AIMessageChunk object in LangChain represents a chunk or partial message generated by an AI model."
          }, 
          "logprobs": null, 
          "finish_reason": "stop"
      }
  ], 
  "usage": {
      "prompt_tokens": 0,
      "completion_tokens": 286, 
      "total_tokens": 286, 
      "completion_tokens_details": {
          "reasoning_tokens": 0
      }
  }, 
  "url_references": [
      "https://python.langchain.com/api_reference/core/messages/langchain_core.messages.ai.add_ai_message_chunks.html"
  ]
}

Unsupported OpenAI Fields

The following are unsupported OpenAI fields.

See chat/completions for more details on these fields.

• model: We don't support changing the base model to process the query. See Tycho for more details on the base model.
• store
• metadata
• frequency_penalty
• logit_bias
• logprobs
• top_logprobs
• max_completion_tokens
• n
• modalities
• audio
• presence_penalty
• seed
• service_tier
• stop
• stream_options
• temperature: Tycho always uses a temperature of 0.
• top_p
• tools
• tool_choice
• parallel_tool_calls
• user

Supported OpenAI Fields

The following are fields that the Lune API supports

• messages: Only user, system, and assistant message types are supported
• stream
• response_format: The Lune API supports OpenAI Structured Output