Call functions - Together AI docs

The two simplest patterns: one tool, one call (simple), and many tools available with the model picking one (multiple).

Simple function calling

Suppose your application has access to a get_current_weather function that takes two named arguments, location and unit:

# Hypothetical function in your app
get_current_weather(location="San Francisco, CA", unit="fahrenheit")

// Hypothetical function in your app
getCurrentWeather({
  location: "San Francisco, CA",
  unit: "fahrenheit",
});

Make this function available to the LLM by passing its description to the tools key alongside the user’s query. Suppose the user asks, “What is the current temperature of New York?”

import json
from together import Together

client = Together()

response = client.chat.completions.create(
    model="Qwen/Qwen2.5-7B-Instruct-Turbo",
    messages=[
        {
            "role": "system",
            "content": "You are a helpful assistant that can access external functions. The responses from these function calls will be appended to this dialogue. Please provide responses based on the information from these function calls.",
        },
        {
            "role": "user",
            "content": "What is the current temperature of New York?",
        },
    ],
    tools=[
        {
            "type": "function",
            "function": {
                "name": "get_current_weather",
                "description": "Get the current weather in a given location",
                "parameters": {
                    "type": "object",
                    "properties": {
                        "location": {
                            "type": "string",
                            "description": "The city and state, e.g. San Francisco, CA",
                        },
                        "unit": {
                            "type": "string",
                            "enum": ["celsius", "fahrenheit"],
                        },
                    },
                },
            },
        }
    ],
)

print(
    json.dumps(
        response.choices[0].message.model_dump()["tool_calls"],
        indent=2,
    )
)

import Together from "together-ai";

const together = new Together();

const response = await together.chat.completions.create({
  model: "Qwen/Qwen2.5-7B-Instruct-Turbo",
  messages: [
    {
      role: "system",
      content:
        "You are a helpful assistant that can access external functions. The responses from these function calls will be appended to this dialogue. Please provide responses based on the information from these function calls.",
    },
    {
      role: "user",
      content: "What is the current temperature of New York?",
    },
  ],
  tools: [
    {
      type: "function",
      function: {
        name: "getCurrentWeather",
        description: "Get the current weather in a given location",
        parameters: {
          type: "object",
          properties: {
            location: {
              type: "string",
              description: "The city and state, e.g. San Francisco, CA",
            },
            unit: {
              type: "string",
              description: "The unit of temperature",
              enum: ["celsius", "fahrenheit"],
            },
          },
        },
      },
    },
  ],
});

console.log(JSON.stringify(response.choices[0].message?.tool_calls, null, 2));

curl -X POST "https://api.together.ai/v1/chat/completions" \
     -H "Authorization: Bearer $TOGETHER_API_KEY" \
     -H "Content-Type: application/json" \
     -d '{
       "model": "Qwen/Qwen2.5-7B-Instruct-Turbo",
       "messages": [
         {
           "role": "system",
           "content": "You are a helpful assistant that can access external functions. The responses from these function calls will be appended to this dialogue. Please provide responses based on the information from these function calls."
         },
         {
           "role": "user",
           "content": "What is the current temperature of New York?"
         }
       ],
       "tools": [
         {
           "type": "function",
           "function": {
             "name": "get_current_weather",
             "description": "Get the current weather in a given location",
             "parameters": {
               "type": "object",
               "properties": {
                 "location": {
                   "type": "string",
                   "description": "The city and state, e.g. San Francisco, CA"
                 },
                 "unit": {
                   "type": "string",
                   "enum": ["celsius", "fahrenheit"]
                 }
               }
             }
           }
         }
       ]
     }'

The model responds with a single function call in the tool_calls array, specifying the function name and arguments needed to get the weather for New York.

JSON

[
  {
    "index": 0,
    "id": "call_aisak3q1px3m2lzb41ay6rwf",
    "type": "function",
    "function": {
      "arguments": "{\"location\":\"New York, NY\",\"unit\":\"fahrenheit\"}",
      "name": "get_current_weather"
    }
  }
]

You can now programmatically execute the function call to answer the user’s question.

Streaming

Function calling also works with streaming responses. When you enable streaming, the model returns tool calls incrementally, accessible from the delta.tool_calls object in each chunk.

from together import Together

client = Together()

tools = [
    {
        "type": "function",
        "function": {
            "name": "get_weather",
            "description": "Get current temperature for a given location.",
            "parameters": {
                "type": "object",
                "properties": {
                    "location": {
                        "type": "string",
                        "description": "City and country e.g. Bogotá, Colombia",
                    }
                },
                "required": ["location"],
                "additionalProperties": False,
            },
            "strict": True,
        },
    }
]

stream = client.chat.completions.create(
    model="Qwen/Qwen3.5-9B",
    reasoning={"enabled": False},
    messages=[{"role": "user", "content": "What's the weather in NYC?"}],
    tools=tools,
    stream=True,
)

for chunk in stream:
    if not chunk.choices:
        continue
    delta = chunk.choices[0].delta
    tool_calls = getattr(delta, "tool_calls", [])
    print(tool_calls)

import Together from "together-ai";

const client = new Together();

const tools = [
  {
    type: "function",
    function: {
      name: "get_weather",
      description: "Get current temperature for a given location.",
      parameters: {
        type: "object",
        properties: {
          location: {
            type: "string",
            description: "City and country e.g. Bogotá, Colombia",
          },
        },
        required: ["location"],
        additionalProperties: false,
      },
      strict: true,
    },
  },
];

const stream = await client.chat.completions.create({
  model: "Qwen/Qwen3.5-9B",
  reasoning: { enabled: false },
  messages: [{ role: "user", content: "What's the weather in NYC?" }],
  tools,
  stream: true,
});

for await (const chunk of stream) {
  const delta = chunk.choices[0]?.delta;
  const toolCalls = delta?.tool_calls ?? [];
  console.log(toolCalls);
}

curl -X POST "https://api.together.ai/v1/chat/completions" \
     -H "Authorization: Bearer $TOGETHER_API_KEY" \
     -H "Content-Type: application/json" \
     -d '{
       "model": "Qwen/Qwen3.5-9B",
        "reasoning": {"enabled": false},
       "messages": [
         {
           "role": "user",
           "content": "What'\''s the weather in NYC?"
         }
       ],
       "tools": [
         {
           "type": "function",
           "function": {
             "name": "get_weather",
             "description": "Get current temperature for a given location.",
             "parameters": {
               "type": "object",
               "properties": {
                 "location": {
                   "type": "string",
                   "description": "City and country e.g. Bogotá, Colombia"
                 }
               },
               "required": ["location"],
               "additionalProperties": false
             },
             "strict": true
           }
         }
       ],
       "stream": true
     }'

The model responds with streamed function calls:

# delta 1
[
  {
    "index": 0,
    "id": "call_fwbx4e156wigo9ayq7tszngh",
    "type": "function",
    "function": {
      "name": "get_weather",
      "arguments": ""
    }
  }
]

# delta 2
[
  {
    "index": 0,
    "function": {
      "arguments": "{\"location\":\"New York City, USA\"}"
    }
  }
]

Tool calls don’t show up in message.content: When a model decides to call a tool, the call lands in message.tool_calls, not in the content string. Some models return null for message.content on a tool-calling turn. Read the call from message.tool_calls[0].function.name and .arguments.

Multiple function calling

Multiple function calling makes several functions available and lets the model choose the best one based on the user’s intent. The model has to understand the request and pick the appropriate tool from the options. The example below provides two tools to the model. The model responds with one tool invocation.

import json
from together import Together

client = Together()

tools = [
    {
        "type": "function",
        "function": {
            "name": "get_current_weather",
            "description": "Get the current weather in a given location",
            "parameters": {
                "type": "object",
                "properties": {
                    "location": {
                        "type": "string",
                        "description": "The city and state, e.g. San Francisco, CA",
                    },
                    "unit": {
                        "type": "string",
                        "enum": ["celsius", "fahrenheit"],
                    },
                },
            },
        },
    },
    {
        "type": "function",
        "function": {
            "name": "get_current_stock_price",
            "description": "Get the current stock price for a given stock symbol",
            "parameters": {
                "type": "object",
                "properties": {
                    "symbol": {
                        "type": "string",
                        "description": "The stock symbol, e.g. AAPL, GOOGL, TSLA",
                    },
                    "exchange": {
                        "type": "string",
                        "description": "The stock exchange (optional)",
                        "enum": ["NYSE", "NASDAQ", "LSE", "TSX"],
                    },
                },
                "required": ["symbol"],
            },
        },
    },
]

response = client.chat.completions.create(
    model="Qwen/Qwen2.5-7B-Instruct-Turbo",
    messages=[
        {
            "role": "user",
            "content": "What's the current price of Apple's stock?",
        },
    ],
    tools=tools,
)

print(
    json.dumps(
        response.choices[0].message.model_dump()["tool_calls"],
        indent=2,
    )
)

import Together from "together-ai";

const together = new Together();

const tools = [
  {
    type: "function",
    function: {
      name: "getCurrentWeather",
      description: "Get the current weather in a given location",
      parameters: {
        type: "object",
        properties: {
          location: {
            type: "string",
            description: "The city and state, e.g. San Francisco, CA",
          },
          unit: {
            type: "string",
            description: "The unit of temperature",
            enum: ["celsius", "fahrenheit"],
          },
        },
      },
    },
  },
  {
    type: "function",
    function: {
      name: "getCurrentStockPrice",
      description: "Get the current stock price for a given stock symbol",
      parameters: {
        type: "object",
        properties: {
          symbol: {
            type: "string",
            description: "The stock symbol, e.g. AAPL, GOOGL, TSLA",
          },
          exchange: {
            type: "string",
            description: "The stock exchange (optional)",
            enum: ["NYSE", "NASDAQ", "LSE", "TSX"],
          },
        },
        required: ["symbol"],
      },
    },
  },
];

const response = await together.chat.completions.create({
  model: "Qwen/Qwen2.5-7B-Instruct-Turbo",
  messages: [
    {
      role: "user",
      content: "What's the current price of Apple's stock?",
    },
  ],
  tools,
});

console.log(JSON.stringify(response.choices[0].message?.tool_calls, null, 2));

curl -X POST "https://api.together.ai/v1/chat/completions" \
     -H "Authorization: Bearer $TOGETHER_API_KEY" \
     -H "Content-Type: application/json" \
     -d '{
       "model": "Qwen/Qwen2.5-7B-Instruct-Turbo",
       "messages": [
         {
           "role": "user",
           "content": "What'\''s the current price of Apple'\''s stock?"
         }
       ],
       "tools": [
         {
           "type": "function",
           "function": {
             "name": "get_current_weather",
             "description": "Get the current weather in a given location",
             "parameters": {
               "type": "object",
               "properties": {
                 "location": {
                   "type": "string",
                   "description": "The city and state, e.g. San Francisco, CA"
                 },
                 "unit": {
                   "type": "string",
                   "enum": ["celsius", "fahrenheit"]
                 }
               }
             }
           }
         },
         {
           "type": "function",
           "function": {
             "name": "get_current_stock_price",
             "description": "Get the current stock price for a given stock symbol",
             "parameters": {
               "type": "object",
               "properties": {
                 "symbol": {
                   "type": "string",
                   "description": "The stock symbol, e.g. AAPL, GOOGL, TSLA"
                 },
                 "exchange": {
                   "type": "string",
                   "description": "The stock exchange (optional)",
                   "enum": ["NYSE", "NASDAQ", "LSE", "TSX"]
                 }
               },
               "required": ["symbol"]
             }
           }
         }
       ]
     }'

In this example, both weather and stock functions are available. The model correctly identifies that the user is asking about stock prices and calls the get_current_stock_price function.

Select a specific tool

To force the model to use a specific tool, pass the tool’s name to the tool_choice parameter:

response = client.chat.completions.create(
    model="Qwen/Qwen3.5-9B",
    messages=[
        {
            "role": "user",
            "content": "What's the current price of Apple's stock?",
        },
    ],
    tools=tools,
    tool_choice={
        "type": "function",
        "function": {"name": "get_current_stock_price"},
    },
)

const response = await together.chat.completions.create({
  model: "Qwen/Qwen3.5-9B",
  messages: [
    {
      role: "user",
      content: "What's the current price of Apple's stock?",
    },
  ],
  tools,
  tool_choice: { type: "function", function: { name: "getCurrentStockPrice" } },
});

curl -X POST "https://api.together.ai/v1/chat/completions" \
     -H "Authorization: Bearer $TOGETHER_API_KEY" \
     -H "Content-Type: application/json" \
     -d '{
       "model": "Qwen/Qwen3.5-9B",
       "messages": [
         {
           "role": "user",
           "content": "What'\''s the current price of Apple'\''s stock?"
         }
       ],
       "tools": [
         {
           "type": "function",
           "function": {
             "name": "get_current_stock_price",
             "description": "Get the current stock price for a given stock symbol",
             "parameters": {
               "type": "object",
               "properties": {
                 "symbol": {
                   "type": "string",
                   "description": "The stock symbol, e.g. AAPL, GOOGL, TSLA"
                 }
               },
               "required": ["symbol"]
             }
           }
         }
       ],
       "tool_choice": {
         "type": "function",
         "function": {
           "name": "get_current_stock_price"
         }
       }
     }'

This forces the model to use the specified function regardless of the user’s phrasing.

`tool_choice` options

The tool_choice parameter controls how the model uses functions. It accepts: String values:

"auto" (default): The model decides whether to call a function or generate a text response.
"none": The model never calls functions, only generates text.
"required": The model must call at least one function.

​Simple function calling

​Streaming

​Multiple function calling

​Select a specific tool

​tool_choice options

Simple function calling

Streaming

Multiple function calling

Select a specific tool

`tool_choice` options