POST
/
v1
/
messages
curl -X POST https://www.anyfast.ai/v1/messages \
  -H "Authorization: Bearer YOUR_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "model": "claude-sonnet-4-20250514",
    "max_tokens": 1024,
    "tools": [
      {
        "name": "get_weather",
        "description": "Get the current weather in a given location",
        "input_schema": {
          "type": "object",
          "properties": {
            "location": {
              "type": "string",
              "description": "The city and state, e.g. San Francisco, CA"
            }
          },
          "required": ["location"]
        }
      }
    ],
    "messages": [
      {
        "role": "user",
        "content": "What is the weather like in San Francisco?"
      }
    ],
    "stream": true
  }'

{
  "id": "msg_01XFDUDYJgAACzvnptvVoYEL",
  "type": "message",
  "role": "assistant",
  "content": [
    {
      "type": "tool_use",
      "id": "toolu_01A09q90qw90lq917835lq9",
      "name": "get_weather",
      "input": {
        "location": "San Francisco, CA"
      }
    }
  ],
  "model": "claude-sonnet-4-20250514",
  "stop_reason": "tool_use",
  "usage": {
    "input_tokens": 384,
    "output_tokens": 62
  }
}
Official documentation: https://docs.anthropic.com/en/docs/build-with-claude/tool-use
Use Anthropic Claude models to perform function calling (tool use) in native format.

​
Request Parameters

​
model
string
required
The model to use. Available models include:
  • claude-haiku-4-5-20251001
  • claude-sonnet-4-20250514
  • claude-opus-4-5-20251101
​
max_tokens
integer
required
The maximum number of tokens to generate before stopping.
​
messages
array
required
Input messages. Each message has a role and content.
​
tools
array
required
An array of tools the model may use. Each tool includes:
  • name (string): The name of the tool
  • description (string): Description of what the tool does
  • input_schema (object): JSON Schema defining the tool’s input parameters
​
stream
boolean
default:"false"
Whether to incrementally stream the response using server-sent events.
​
temperature
number
default:"1"
Amount of randomness injected into the response. Ranges from 0.0 to 1.0.

​
Response

​
id
string
Unique identifier for the message.
​
type
string
Object type, which is message.
​
content
array
Content generated by the model. When tool use is triggered, includes tool_use blocks.
​
stop_reason
string
The reason the model stopped. Will be tool_use when the model wants to call a tool.
curl -X POST https://www.anyfast.ai/v1/messages \
  -H "Authorization: Bearer YOUR_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "model": "claude-sonnet-4-20250514",
    "max_tokens": 1024,
    "tools": [
      {
        "name": "get_weather",
        "description": "Get the current weather in a given location",
        "input_schema": {
          "type": "object",
          "properties": {
            "location": {
              "type": "string",
              "description": "The city and state, e.g. San Francisco, CA"
            }
          },
          "required": ["location"]
        }
      }
    ],
    "messages": [
      {
        "role": "user",
        "content": "What is the weather like in San Francisco?"
      }
    ],
    "stream": true
  }'

{
  "id": "msg_01XFDUDYJgAACzvnptvVoYEL",
  "type": "message",
  "role": "assistant",
  "content": [
    {
      "type": "tool_use",
      "id": "toolu_01A09q90qw90lq917835lq9",
      "name": "get_weather",
      "input": {
        "location": "San Francisco, CA"
      }
    }
  ],
  "model": "claude-sonnet-4-20250514",
  "stop_reason": "tool_use",
  "usage": {
    "input_tokens": 384,
    "output_tokens": 62
  }
}