Chat Completions API

Send an ordered messages array to the Chat Completions endpoint and read the reply from choices[0].message.content. Use a model API key with access to the model you select.

POST https://api2.laozhang.ai/v1/chat/completions

Make a request

Create a key in Token management and set it as the LAOZHANG_API_KEY environment variable. The examples use gpt-5.4-mini; check model access for your token group in Models and pricing. Requests use Authorization: Bearer authentication and a JSON body containing model and messages.

cURL
Python

curl --fail-with-body --max-time 120 \
  "https://api2.laozhang.ai/v1/chat/completions" \
  -H "Authorization: Bearer $LAOZHANG_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "model": "gpt-5.4-mini",
    "messages": [
      {"role": "user", "content": "Reply only with: connected"}
    ]
  }'

Install the SDK with python -m pip install openai.

import os
from openai import OpenAI

client = OpenAI(
    api_key=os.environ["LAOZHANG_API_KEY"],
    base_url="https://api2.laozhang.ai/v1",
    timeout=120.0,
    max_retries=0,
)
response = client.chat.completions.create(
    model="gpt-5.4-mini",
    messages=[{"role": "user", "content": "Reply only with: connected"}],
)
print(response.choices[0].message.content)

The reply to this prompt should be connected. Replace the prompt with your application’s message once the client is configured.

Request fields

Field	Description
`model`	Required. Exact model ID available to your token group.
`messages`	Required. Messages in conversation order.
`temperature`, `top_p`	Optional sampling controls, where supported by the model.
`max_completion_tokens`	Output limit for models that accept this field.
`max_tokens`	Output limit used by some models; do not send both limit fields.
`response_format`	Output-format settings for models with JSON or structured-output support.
`tools`, `tool_choice`	Tool definitions and selection settings for models with tool-calling support.

Start with model and messages. Optional fields and accepted values depend on the model; a request rejected for an unsupported parameter needs a field change before you retry it. See the official Chat Completions reference for upstream field definitions.

Messages and conversation history

Each message has a role and content. Use user for user input and assistant for previous model replies. Send the history your application needs with each request:

[
  {"role": "user", "content": "My project is called Cedar."},
  {"role": "assistant", "content": "How can I help with Cedar?"},
  {"role": "user", "content": "Suggest a short tagline for it."}
]

Instruction roles such as system or developer, tool messages, and multimodal content depend on the selected model. A text content string is sufficient for the basic request above.

Read the response

A text response contains a choices array. This shortened example shows the fields to read:

{
  "choices": [
    {
      "index": 0,
      "message": {"role": "assistant", "content": "connected"},
      "finish_reason": "stop"
    }
  ]
}

Read message.content for the answer and finish_reason to see why generation ended. A length finish reason means the reply reached an output or context limit; shorten the input or adjust the model’s supported output limit if you need a complete answer. For a model that supports tool calls, the reply may contain message.tool_calls instead of ordinary text. Preserve those calls and their matching results when continuing the conversation. Token counts may appear in usage; use call logs to review account charges.

Handle errors

Status	Action
400	Correct invalid fields, field types, or an input that exceeds the model’s limit.
401	Check the Bearer header and API key.
403	Check token-group permissions and account restrictions.
404	Check the endpoint and exact model ID.
429	Read the error body for rate, concurrency, capacity, or balance limits.
5xx	Check call logs and retry temporary failures with bounded backoff.

For a client timeout, check whether the request appears in call logs before sending it again. The Python example disables automatic retries; add retry handling deliberately in your application. When contacting support, include the request time, endpoint, model, token group, and error message with credentials removed. Never send your API key.

Core APIs

Model Guides

Make a request

Request fields

Messages and conversation history

Read the response

Handle errors

​Make a request

​Request fields

​Messages and conversation history

​Read the response

​Handle errors

​Related documentation

Make a request

Request fields

Messages and conversation history

Read the response

Handle errors

Related documentation