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POST
/
v1
/
messages
Create a Message
curl --request POST \
  --url https://www.anyfast.ai/v1/messages \
  --header 'Content-Type: application/json' \
  --data '
{
  "model": "claude-sonnet-5",
  "messages": [
    {
      "role": "user",
      "content": "Hello, Claude!"
    }
  ],
  "max_tokens": 1024,
  "system": "<string>",
  "metadata": {
    "user_id": "<string>"
  },
  "stop_sequences": [
    "<string>"
  ],
  "temperature": 1,
  "top_p": 0.5,
  "top_k": 1,
  "stream": false,
  "tools": [
    {
      "name": "<string>",
      "input_schema": {},
      "description": "<string>"
    }
  ],
  "tool_choice": {
    "name": "<string>"
  },
  "output_config": {
    "effort": "high"
  },
  "thinking": {}
}
'
{
  "id": "msg_01XFDUDYJgAACzvnptvVoYEL",
  "type": "message",
  "role": "assistant",
  "content": [
    {
      "type": "text",
      "text": "Hello! How can I help you today?"
    }
  ],
  "model": "claude-sonnet-5",
  "usage": {
    "input_tokens": 123,
    "output_tokens": 123,
    "cache_creation_input_tokens": 123,
    "cache_read_input_tokens": 123
  },
  "stop_sequence": "<string>"
}

Body

application/json
​
model
enum<string>
required

Model ID.

Available options:
claude-sonnet-5
Example:

"claude-sonnet-5"

​
messages
object[]
required

Input messages. Each message has a role and content.

Minimum array length: 1
Example:
[
  {
    "role": "user",
    "content": "Hello, Claude!"
  }
]
​
max_tokens
integer
required

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

Required range: 1 <= x <= 128000
Example:

1024

​
system

System prompt. Provides context and instructions to Claude.

​
metadata
object

An object describing metadata about the request.

​
stop_sequences
string[]

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

​
temperature
number
default:1

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

Required range: 0 <= x <= 1
Example:

1

​
top_p
number

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

Required range: 0 <= x <= 1
​
top_k
integer

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

Required range: x >= 0
​
stream
boolean
default:false

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

​
tools
object[]

Definitions of tools that the model may use.

​
tool_choice
object

How the model should use the provided tools.

​
output_config
object

Output controls for models that support adaptive thinking effort.

​
thinking
object

Adaptive thinking configuration. Claude Sonnet 5 uses adaptive thinking by default; use output_config.effort to control depth. Manual extended thinking is not supported.

Response

Message created successfully

​
id
string
required
Example:

"msg_01XFDUDYJgAACzvnptvVoYEL"

​
type
string
required
Example:

"message"

​
role
string
required
Example:

"assistant"

​
content
object[]
required
Example:
[
  {
    "type": "text",
    "text": "Hello! How can I help you today?"
  }
]
​
model
string
required
Example:

"claude-sonnet-5"

​
stop_reason
enum<string>
required

Includes refusal for requests that the model declines.

Available options:
end_turn,
max_tokens,
stop_sequence,
tool_use,
refusal,
null
​
usage
object
required
​
stop_sequence
string | null