ik_llama.cpp/examples/server/function_calls.md

Function Calling Support

This document describes the function calling format supported by the ik_llama.cpp server implementation.

Overview

The server supports multiple native function calling formats including Kimi-K2, Qwen3 (XML), and DeepSeek R1. All function calls are automatically detected and converted to OpenAI-compatible responses.

⚠️ Model Requirements: Function calling support is enabled for the following model types:

• Kimi-K2 models: Models containing "kimi-k2" or "kimi_k2" in the model name
• Qwen3 models: Models containing "qwen3", "qwen-3", or "qwen_3" in the model name
• DeepSeek R1 models: Models containing "deepseek-r1", "deepseek_r1", or similar patterns

Other models will not have tool injection or function call parsing enabled.

Supported Formats

Kimi-K2 Native Token Format

Detection Pattern: <|tool_calls_section_begin|>...<|tool_calls_section_end|>

Structure:

<|tool_calls_section_begin|>
<|tool_call_begin|>
functions.{name}:{index}<|tool_call_argument_begin|>
{JSON arguments}
<|tool_call_end|>
<|tool_calls_section_end|>

Example:

<|tool_calls_section_begin|>
<|tool_call_begin|>
functions.get_weather:0<|tool_call_argument_begin|>
{"location": "Tokyo"}
<|tool_call_end|>
<|tool_calls_section_end|>

Notes:

• Native Kimi-K2 token format
• Multiple function calls supported with different indices
• Arguments are JSON objects
• Function names follow functions.{name}:{index} pattern

XML-Style Format (Fallback)

Detection Pattern: <tool_call>...<invoke name="...">...<parameter name="...">...</parameter>...</invoke></tool_call>

Structure:

<tool_call>
<invoke name="{function_name}">
<parameter name="{param_name}">{param_value}</parameter>
<parameter name="{param_name}">{param_value}</parameter>
</invoke>
</tool_call>

Example:

<tool_call>
<invoke name="Write">
<parameter name="file_path">/path/to/file.txt</parameter>
<parameter name="content">File content here</parameter>
</invoke>
</tool_call>

Notes:

• XML-style format as fallback when model generates this format instead of token format
• Parameters are extracted as key-value pairs
• Automatically converted to JSON arguments

DeepSeek R1 Native Format

Detection Pattern: <｜tool▁calls▁begin｜>...<｜tool▁calls▁end｜>

Structure:

<｜tool▁calls▁begin｜>
<｜tool▁call▁begin｜>
function<｜tool▁sep｜>{function_name}
```json
{JSON arguments}

<｜tool▁call▁end｜> <｜tool▁calls▁end｜>

**Example:**

<｜tool▁calls▁begin｜> <｜tool▁call▁begin｜> function<｜tool▁sep｜>get_weather

{"location": "Tokyo"}

<｜tool▁call▁end｜> <｜tool▁calls▁end｜>

**Notes:**
- Native DeepSeek R1 format ported from original llama.cpp
- Supports reasoning with `<think>...</think>` tags (automatically extracted)
- Multiple function calls supported with separate call blocks
- JSON arguments are contained within markdown code blocks

## OpenAI-Compatible Output

The native format is converted to the standard OpenAI function calling response:

```json
{
  "choices": [
    {
      "finish_reason": "tool_calls",
      "message": {
        "role": "assistant",
        "content": "filtered_content_without_function_calls",
        "tool_calls": [
          {
            "id": "functions.get_weather:0",
            "type": "function",
            "function": {
              "name": "get_weather",
              "arguments": "{\"location\": \"Tokyo\"}"
            }
          }
        ]
      }
    }
  ]
}

Implementation Details

Content Filtering

When function calls are detected:

• Function call syntax is removed from content
• Tool calls are extracted into separate array
• Content is cleaned for display

Error Handling

• Missing tokens in format returns empty array
• Malformed structure returns empty array
• Parser gracefully handles invalid JSON in arguments

Usage with Tools Parameter

To enable function calling, include the tools parameter in your request:

{
  "model": "kimi-k2",
  "messages": [
    {
      "role": "user",
      "content": "What's the weather in Tokyo?"
    }
  ],
  "tools": [
    {
      "type": "function",
      "function": {
        "name": "get_weather",
        "description": "Get weather information for a location",
        "parameters": {
          "type": "object",
          "properties": {
            "location": {
              "type": "string",
              "description": "The city and state, e.g. San Francisco, CA"
            }
          },
          "required": ["location"]
        }
      }
    }
  ]
}

Model Compatibility

• Kimi-K2 models: Native support with token format
• Qwen3 models: Native support with XML format (Hermes-style)
• DeepSeek R1 models: Native support with reasoning and function call format (ported from original llama.cpp)
• Other models: No function calling support

Testing

Test files are provided to verify function calling:

• test-function-calls.cpp - Unit tests for the native Kimi-K2 format
  • Tests native token format parsing
  • Tests multiple function calls
  • Tests error handling and malformed input

File Structure

• function_calls.hpp - Parser implementation for native Kimi-K2 format
• utils.hpp - Integration with server (includes function_calls.hpp)
• server.cpp - Response formatting and content filtering