Create a Message

Send a structured list of input messages with text and/or image content, and Claude Sonnet 5 will generate the next message in the conversation.

Request body

model'claude-sonnet-5' required

Model ID.

max_tokensinteger required

The maximum number of tokens to generate before stopping. Claude Sonnet 5 supports up to 128K output tokens.

stop_sequencesstring[]

Custom text sequences that will cause the model to stop generating.

temperaturenumber

Amount of randomness injected into the response. On Claude Sonnet 5, non-default values return a 400 error.

top_pnumber

Use nucleus sampling. On Claude Sonnet 5, non-default values return a 400 error.

top_kinteger

Only sample from the top K options for each subsequent token. On Claude Sonnet 5, non-default values return a 400 error.

streamboolean

Whether to incrementally stream the response using server-sent events.

Example request

{
  "model": "claude-sonnet-5",
  "messages": [
    {
      "role": "user",
      "content": "Hello, Claude!"
    }
  ],
  "max_tokens": 1024,
  "temperature": 1
}

Response

Message created successfully

idstring required

typestring required

rolestring required

modelstring required

stop_reasonstring required

Includes refusal for requests that the model declines.

stop_sequencestring nullable

Example response

{
  "id": "msg_01XFDUDYJgAACzvnptvVoYEL",
  "type": "message",
  "role": "assistant",
  "content": [
    {
      "type": "text",
      "text": "Hello! How can I help you today?"
    }
  ],
  "model": "claude-sonnet-5"
}

v1

Create a Message

Request body

Example request

Response

Example response