Create a chat completion

POST

chat

completions

curl https://inference.tokenchange.io/v1/chat/completions \
  -H "Content-Type: application/json" \
  -H "Authorization: Bearer $TOKENCHANGE_API_KEY" \
  -d '{
    "model": "<model-slug>",
    "stream": true,
    "stream_options": { "include_usage": true },
    "messages": [
      { "role": "system", "content": "You are a concise assistant." },
      { "role": "user", "content": "What is the capital of France?" }
    ]
  }'

stream = client.chat.completions.create(
    model="<model-slug>",
    messages=[
        {"role": "system", "content": "You are a concise assistant."},
        {"role": "user", "content": "What is the capital of France?"},
    ],
    stream=True,
    stream_options={"include_usage": True},
)

for chunk in stream:
    if chunk.choices and chunk.choices[0].delta.content:
        print(chunk.choices[0].delta.content, end="")
    if chunk.usage:
        print("\n", chunk.usage)

const stream = await client.chat.completions.create({
  model: "<model-slug>",
  messages: [
    { role: "system", content: "You are a concise assistant." },
    { role: "user", content: "What is the capital of France?" },
  ],
  stream: true,
  stream_options: { include_usage: true },
});

for await (const chunk of stream) {
  process.stdout.write(chunk.choices[0]?.delta?.content ?? "");
  if (chunk.usage) console.log("\n", chunk.usage);
}

data: {"id":"chatcmpl-123","object":"chat.completion.chunk","created":1767225600,"model":"<model-slug>","choices":[{"index":0,"delta":{"role":"assistant","content":"The"},"finish_reason":null}]}

data: {"id":"chatcmpl-123","object":"chat.completion.chunk","created":1767225600,"model":"<model-slug>","choices":[{"index":0,"delta":{"content":" capital of France is Paris."},"finish_reason":"stop"}]}

data: {"id":"chatcmpl-123","object":"chat.completion.chunk","created":1767225600,"model":"<model-slug>","choices":[],"usage":{"prompt_tokens":24,"completion_tokens":8,"total_tokens":32,"prompt_tokens_details":{"cached_tokens":0}}}

data: [DONE]

Streams a chat completion from one of the model’s endpoints. The request and response follow the OpenAI chat completions format.

Request

string

required

Bearer ask_..., an inference key.

string

required

A model slug from the catalog, or <model-slug>/ep/<endpoint> to pin one endpoint.

object[]

required

The conversation, in the OpenAI messages format.

boolean

required

Must be true.

integer

Maximum tokens to generate. At least 1.

number

Sampling temperature, from 0 to 2.

boolean

default:"false"

Set to true to receive token usage in the final chunk.

string

Requests with the same key are routed to the same endpoint so its prompt cache is reused. See Prompt caching.

object

Price options. See Price options.

Show properties

number | string

Highest input price you accept, in USD per million tokens.

number | string

Highest output price you accept, in USD per million tokens.

string

"price" to try the cheapest endpoints first.

Other OpenAI chat completion fields, such as tools, tool_choice, response_format, top_p, stop and seed, are passed to the endpoint unchanged. Support depends on the endpoint’s capabilities.

curl https://inference.tokenchange.io/v1/chat/completions \
  -H "Content-Type: application/json" \
  -H "Authorization: Bearer $TOKENCHANGE_API_KEY" \
  -d '{
    "model": "<model-slug>",
    "stream": true,
    "stream_options": { "include_usage": true },
    "messages": [
      { "role": "system", "content": "You are a concise assistant." },
      { "role": "user", "content": "What is the capital of France?" }
    ]
  }'

stream = client.chat.completions.create(
    model="<model-slug>",
    messages=[
        {"role": "system", "content": "You are a concise assistant."},
        {"role": "user", "content": "What is the capital of France?"},
    ],
    stream=True,
    stream_options={"include_usage": True},
)

for chunk in stream:
    if chunk.choices and chunk.choices[0].delta.content:
        print(chunk.choices[0].delta.content, end="")
    if chunk.usage:
        print("\n", chunk.usage)

const stream = await client.chat.completions.create({
  model: "<model-slug>",
  messages: [
    { role: "system", content: "You are a concise assistant." },
    { role: "user", content: "What is the capital of France?" },
  ],
  stream: true,
  stream_options: { include_usage: true },
});

for await (const chunk of stream) {
  process.stdout.write(chunk.choices[0]?.delta?.content ?? "");
  if (chunk.usage) console.log("\n", chunk.usage);
}

Response

The response is a stream of server-sent events. Each event’s data is a JSON chat completion chunk, and the stream ends with data: [DONE].

string

Identifier for the completion.

string

chat.completion.chunk.

string

The model you requested.

object[]

Show properties

integer

Choice index.

object

The new content in this chunk, such as role and content.

string | null

Why generation stopped, in the last chunk of a choice.

object | null

Only sent when stream_options.include_usage is true, in the final chunk.

Show properties

integer

Prompt tokens, including cached tokens.

integer

Generated tokens.

integer

Sum of prompt and completion tokens.

integer

Prompt tokens served from the endpoint’s prompt cache.

data: {"id":"chatcmpl-123","object":"chat.completion.chunk","created":1767225600,"model":"<model-slug>","choices":[{"index":0,"delta":{"role":"assistant","content":"The"},"finish_reason":null}]}

data: {"id":"chatcmpl-123","object":"chat.completion.chunk","created":1767225600,"model":"<model-slug>","choices":[{"index":0,"delta":{"content":" capital of France is Paris."},"finish_reason":"stop"}]}

data: {"id":"chatcmpl-123","object":"chat.completion.chunk","created":1767225600,"model":"<model-slug>","choices":[],"usage":{"prompt_tokens":24,"completion_tokens":8,"total_tokens":32,"prompt_tokens_details":{"cached_tokens":0}}}

data: [DONE]

The values above are illustrative. Chunks come from the endpoint that served the request, so extra fields it sends, such as reasoning content, are passed through.

Errors during a stream

Errors before the stream starts return an HTTP error status. See Errors. If the endpoint fails after the stream has started, you receive an error event and then data: [DONE]:

data: {"error":{"message":"upstream stream interrupted","type":"server_error"}}

Output delivered before the error is billed.

⌘I

curl https://inference.tokenchange.io/v1/chat/completions \
  -H "Content-Type: application/json" \
  -H "Authorization: Bearer $TOKENCHANGE_API_KEY" \
  -d '{
    "model": "<model-slug>",
    "stream": true,
    "stream_options": { "include_usage": true },
    "messages": [
      { "role": "system", "content": "You are a concise assistant." },
      { "role": "user", "content": "What is the capital of France?" }
    ]
  }'

stream = client.chat.completions.create(
    model="<model-slug>",
    messages=[
        {"role": "system", "content": "You are a concise assistant."},
        {"role": "user", "content": "What is the capital of France?"},
    ],
    stream=True,
    stream_options={"include_usage": True},
)

for chunk in stream:
    if chunk.choices and chunk.choices[0].delta.content:
        print(chunk.choices[0].delta.content, end="")
    if chunk.usage:
        print("\n", chunk.usage)

const stream = await client.chat.completions.create({
  model: "<model-slug>",
  messages: [
    { role: "system", content: "You are a concise assistant." },
    { role: "user", content: "What is the capital of France?" },
  ],
  stream: true,
  stream_options: { include_usage: true },
});

for await (const chunk of stream) {
  process.stdout.write(chunk.choices[0]?.delta?.content ?? "");
  if (chunk.usage) console.log("\n", chunk.usage);
}

data: {"id":"chatcmpl-123","object":"chat.completion.chunk","created":1767225600,"model":"<model-slug>","choices":[{"index":0,"delta":{"role":"assistant","content":"The"},"finish_reason":null}]}

data: {"id":"chatcmpl-123","object":"chat.completion.chunk","created":1767225600,"model":"<model-slug>","choices":[{"index":0,"delta":{"content":" capital of France is Paris."},"finish_reason":"stop"}]}

data: {"id":"chatcmpl-123","object":"chat.completion.chunk","created":1767225600,"model":"<model-slug>","choices":[],"usage":{"prompt_tokens":24,"completion_tokens":8,"total_tokens":32,"prompt_tokens_details":{"cached_tokens":0}}}

data: [DONE]

​Request

​Response

​Errors during a stream

Request

Response

Errors during a stream