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: Multiple formats supported with automatic fallback

⚠️ Critical Implementation Note: DeepSeek R1 models generate different formats depending on context. The parser handles all variants automatically.

Format 1: Full Native Format (Primary)

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

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

<｜tool▁call▁end｜> <｜tool▁calls▁end｜>

#### Format 2: Simplified Format (Fallback)
**Pattern:** `function<{function_name}>`

function<get_weather>

{"location": "Tokyo"}

#### Format 3: Tools Array Format (New - July 2025)
**Pattern:** `function\n```json\n{"tools": [...]}`

function

{
  "tools": [
    {
      "name": "get_weather",
      "arguments": {
        "location": "Tokyo"
      }
    },
    {
      "name": "Read",
      "arguments": {
        "file_path": "/path/to/file.java"
      }
    }
  ]
}

#### Format 4: XML Wrapped Format (New - July 2025)
**Pattern:** `<tool_call>function</think>{function_name}\n```json\n{...}\n```</tool_call>`

<tool_call> functionRead

{
  "file_path": "/path/to/example.txt"
}

</tool_call>

**Notes:**
- XML wrapper contains function name after `function</think>`
- Single function call per XML block
- JSON arguments within ```json``` code blocks
- Handles reasoning text before function name

**Examples:**

Format 1 (Full):

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

{"location": "Tokyo"}

<｜tool▁call▁end｜> <｜tool▁calls▁end｜>

Format 2 (Simplified):

function

{"file_path": "/path/to/file.txt"}

Format 3 (Tools Array):

function

{
  "tools": [
    {
      "name": "Read",
      "arguments": {
        "file_path": "/path/to/example/SystemProcessor.java"
      }
    },
    {
      "name": "Edit", 
      "arguments": {
        "file_path": "/path/to/file.java",
        "old_string": "old code",
        "new_string": "new code"
      }
    }
  ]
}

Format 4 (XML Wrapped):

<tool_call> functionCompleteTask

{
  "status": "completed"
}

</tool_call>

**Implementation Notes:**
- **Reasoning Support**: All formats support `<think>...</think>` reasoning tags (automatically extracted)
- **Multiple Tool Calls**: Format 1 & 2 use separate blocks, Format 3 uses array structure, Format 4 uses single XML block
- **Automatic Detection**: Parser tries formats in order: Format 3 → Format 4 → Format 1 → Format 2
- **Original llama.cpp Base**: Implementation follows original llama.cpp patterns exactly
- **Status**: All formats ✅ Working (July 2025 update)

## 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

Comprehensive test suite for all supported formats:

Unit Tests

• File: tests/test-function-calls.cpp
• Coverage: All supported model formats (Kimi-K2, Qwen3, DeepSeek R1)
• Test Types:
  • Native format parsing for each model type
  • Multiple function calls
  • Error handling and malformed input
  • Streaming and non-streaming responses
  • Content extraction and cleaning
  • OpenAI-compatible output generation

DeepSeek R1 Specific Tests

• Format 1 Tests: Full native format with separators ✅
• Format 2 Tests: Simplified format without separators ✅
• Format 3 Tests: Tools array format ✅ (Fixed July 2025)
• Format 4 Tests: XML wrapped format ✅ (Added July 2025)
• Integration Tests: Server-to-parser call chain verification
• Regression Tests: Ensure existing formats continue working

Running Tests

# Build tests
cd build && make test-function-calls -j$(nproc)

# Run all function call tests
./bin/test-function-calls

# Run DeepSeek R1 specific tests
./bin/test-function-calls | grep -E "(DeepSeek|tool_calls_count)"

# Check Format 3 specific issues
./bin/test-function-calls | grep -A5 -B5 "Real failing format"

Test Status

• Kimi-K2: ✅ All tests passing
• Qwen3 XML: ✅ All tests passing
• DeepSeek R1 Format 1 & 2: ✅ All tests passing
• DeepSeek R1 Format 3: ✅ All tests passing (Fixed July 2025)
• DeepSeek R1 Format 4: ✅ All tests passing (Added July 2025)

File Structure

Server Integration

• examples/server/server.cpp - Main server entry point, calls parse_chat_message_incremental()
• examples/server/function_calls.hpp - Server-side parser creation and integration
• examples/server/utils.hpp - Server utilities (includes function_calls.hpp)

Core Parsing Engine

• common/chat-parser.cpp - Main parser routing, delegates to model-specific parsers
• common/chat-parser.h - Parser interface and JSON parsing infrastructure
• common/chat.cpp - Model-specific parsing implementations:
  • common_chat_parse_kimi_k2() - Kimi-K2 native format
  • common_chat_parse_qwen3() - Qwen3 XML format
  • common_chat_parse_deepseek_r1() - DeepSeek R1 multiple formats
  • parse_deepseek_r1_tools_array() - Format 3 tools array parser
  • parse_deepseek_r1_xml_wrapped() - Format 4 XML wrapper parser
• common/chat.h - Function declarations and model detection

Testing

• tests/test-function-calls.cpp - Comprehensive unit tests for all formats
• tests/get-model.cpp - Test utilities for model loading

Integration Flow

server.cpp:2832
  ↓ parse_chat_message_incremental(generated_text, false, modelname)
function_calls.hpp:94-95  
  ↓ common_chat_msg_parser.parse()
chat-parser.cpp:140
  ↓ model detection → specific parser
chat.cpp
  ↓ common_chat_parse_deepseek_r1() / kimi_k2() / qwen3()
  ↓ Format detection → regex matching → JSON parsing → tool_calls array

Key Implementation Files

• DeepSeek R1 Format 3: common/chat.cpp:291-332 (parse_deepseek_r1_tools_array)
• DeepSeek R1 Format 4: common/chat.cpp:335-374 (parse_deepseek_r1_xml_wrapped)
• Exception handling: common/chat.cpp:222-289 (Format 3 → 4 → 1 → 2 fallback chain)
• Model detection: common/chat.cpp (is_deepseek_r1_model, is_qwen3_model, etc.)
• Comprehensive tests: tests/test-function-calls.cpp (All formats with TDD coverage)