Text generation

Two OpenAI protocols are available for text. Use models with kind: text from GET /v1/models.

Chat Completions

POST /v1/chat/completions

Every field of the protocol is forwarded to the model as sent — tools, tool_choice, response_format, logprobs, seed, stop and the rest. Whether a model honours a field is up to the model.

string

required

A model id, for example deepseek/deepseek-v4-flash.

object[]

required

The conversation. role: system, developer, user, assistant or tool. content: text, or an array of parts (text, image_url, …).

integer

Cap on output tokens, reasoning included.

boolean

default:"false"

number

From 0 to 2.

string

minimal, low, medium or high.

object[]

string | object

none, auto, required, or a specific tool.

The response is a standard chat.completion object with choices (message, finish_reason: stop, length, tool_calls, content_filter) and usage. completion_tokens includes hidden reasoning tokens.

Tool calling

curl https://b2b.api.ascn.ai/api/ai-gateway/v1/chat/completions \
  -H "X-API-KEY: $ASCN_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "model": "openai/gpt-4o-mini",
    "messages": [{"role": "user", "content": "What is the weather in Berlin?"}],
    "tools": [{
      "type": "function",
      "function": {
        "name": "get_weather",
        "description": "Current weather for a city.",
        "parameters": {"type": "object", "properties": {"city": {"type": "string"}}, "required": ["city"]}
      }
    }]
  }'

Responses

POST /v1/responses

For code written against client.responses.create. Required fields are model and input (a string or an array of messages); also instructions, max_output_tokens, temperature, tools, stream.

Responses are not stored. previous_response_id and retrieving a response later are not supported — send the whole conversation in input.

response = client.responses.create(
    model="openai/gpt-4o-mini",
    input="Summarise the CAP theorem in three bullets.",
    max_output_tokens=400,
)
print(response.output_text)

Streaming

Set "stream": true to receive Server-Sent Events. The stream ends with data: [DONE].

Chat Completions — stream_options.include_usage is always forced on; the final chunk carries usage.
Responses — events response.output_text.delta, …, response.completed; usage is in response.completed.

Use streaming for long answers. A long non-streamed answer may be rejected with streaming_required.

stream = client.chat.completions.create(
    model="anthropic/claude-haiku-4.5",
    max_tokens=1024,
    messages=[{"role": "user", "content": "Explain mixture-of-experts in one paragraph."}],
    stream=True,
)
for chunk in stream:
    if chunk.choices and chunk.choices[0].delta.content:
        print(chunk.choices[0].delta.content, end="")

A stream that has started cannot switch to another backend. If the backend fails mid-answer, the stream ends with data: {"error": {…}} followed by data: [DONE] — treat what arrived as a partial answer.

Getting Started

Guides

API

Chat Completions

Responses

Streaming

​Chat Completions

​Responses

​Streaming

Chat Completions

Responses

Streaming