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Create Chat Completion

POST /v1/chat/completions
Generates model responses from a message list and supports both non-streaming and streaming output. This page only documents common behavior revalidated against Crazyrouter production on 2026-03-23.

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Authentication

Authorization: Bearer YOUR_API_KEY

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Core parameters

ParameterTypeRequiredMeaning
modelstringYesModel name such as gpt-5.4, claude-sonnet-4-6, or gemini-3-pro-preview
messagesarrayYesMessage list
streambooleanNoWhether to stream output
max_tokensintegerNoMaximum output tokens
temperaturenumberNoSampling temperature
response_formatobjectNoStructured output constraint
toolsarrayNoTool list
tool_choicestring|objectNoTool-selection strategy
stream_optionsobjectNoStreaming extras such as include_usage
Optional parameter support varies by model. Client code should rely on the stable common fields first rather than assuming every model supports the same advanced options.

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Non-streaming request

cURL
curl https://crazyrouter.com/v1/chat/completions \
  -H "Content-Type: application/json" \
  -H "Authorization: Bearer YOUR_API_KEY" \
  -d '{
    "model": "gpt-5.4",
    "messages": [
      {
        "role": "system",
        "content": "You are a helpful assistant."
      },
      {
        "role": "user",
        "content": "Explain artificial intelligence in one sentence."
      }
    ],
    "max_tokens": 64
  }'
Typical production shape: 
{
  "object": "chat.completion",
  "model": "gpt-5.4",
  "choices": [
    {
      "message": {
        "role": "assistant",
        "content": "...",
        "reasoning_content": null,
        "tool_calls": null
      },
      "finish_reason": "stop"
    }
  ]
}

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Important interpretation

  • message.content is the most stable final-text field
  • message.tool_calls only appears when the model is requesting tool execution
  • message.reasoning_content may exist as a key, but should not currently be treated as guaranteed usable content

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Streaming request

cURL
curl https://crazyrouter.com/v1/chat/completions \
  -H "Content-Type: application/json" \
  -H "Authorization: Bearer YOUR_API_KEY" \
  -d '{
    "model": "gpt-5.4",
    "messages": [
      {
        "role": "user",
        "content": "Explain AI in one short sentence."
      }
    ],
    "stream": true,
    "stream_options": {
      "include_usage": true
    },
    "max_tokens": 64
  }'
This production recheck confirmed that:
  • streaming returns chat.completion.chunk
  • SSE chunks are sent as data: ...
  • the stream still ends with data: [DONE]
Observed SSE shape: 
data: {"object":"chat.completion.chunk","model":"gpt-5.4","choices":[{"delta":{"role":"assistant","content":"AI","reasoning_content":null,"tool_calls":null}}]}

data: [DONE]

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Python example

Python
from openai import OpenAI

client = OpenAI(
    api_key="YOUR_API_KEY",
    base_url="https://crazyrouter.com/v1"
)

stream = client.chat.completions.create(
    model="gpt-5.4",
    messages=[
        {"role": "user", "content": "Explain AI in one short sentence."}
    ],
    stream=True,
    stream_options={"include_usage": True},
    max_tokens=64
)

for chunk in stream:
    delta = chunk.choices[0].delta
    if delta.content is not None:
        print(delta.content, end="")

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Current recommendation

  • For normal text chat, use /v1/chat/completions
  • For reasoning summaries or OpenAI-style web search, prefer /v1/responses
  • For more specific capability guarantees, use the dedicated capability pages rather than this generic endpoint page
Related pages: