openhands/llm/fn_call_converter.py

"""Convert function calling messages to non-function calling messages and vice versa.

This will inject prompts so that models that doesn't support function calling
can still be used with function calling agents.

We follow format from: https://docs.litellm.ai/docs/completion/function_call
"""

import copy
import json
import re
import sys
from typing import Iterable

from litellm import ChatCompletionToolParam

from openhands.core.exceptions import (
    FunctionCallConversionError,
    FunctionCallValidationError,
)
from openhands.llm.tool_names import (
    BROWSER_TOOL_NAME,
    EXECUTE_BASH_TOOL_NAME,
    FINISH_TOOL_NAME,
    STR_REPLACE_EDITOR_TOOL_NAME,
)

# Inspired by: https://docs.together.ai/docs/llama-3-function-calling#function-calling-w-llama-31-70b
SYSTEM_PROMPT_SUFFIX_TEMPLATE = """
You have access to the following functions:

{description}

If you choose to call a function ONLY reply in the following format with NO suffix:

<function=example_function_name>
<parameter=example_parameter_1>value_1</parameter>
<parameter=example_parameter_2>
This is the value for the second parameter
that can span
multiple lines
</parameter>
</function>

<IMPORTANT>
Reminder:
- Function calls MUST follow the specified format, start with <function= and end with </function>
- Required parameters MUST be specified
- Only call one function at a time
- You may provide optional reasoning for your function call in natural language BEFORE the function call, but NOT after.
- If there is no function call available, answer the question like normal with your current knowledge and do not tell the user about function calls
</IMPORTANT>
"""

STOP_WORDS = ['</function']


def refine_prompt(prompt: str) -> str:
    if sys.platform == 'win32':
        return prompt.replace('bash', 'powershell')
    return prompt


# NOTE: we need to make sure these examples are always in-sync with the tool interface designed in openhands/agenthub/codeact_agent/function_calling.py

# Example snippets for each tool
TOOL_EXAMPLES = {
    'execute_bash': {
        'check_dir': """
ASSISTANT: Sure! Let me first check the current directory:
<function=execute_bash>
<parameter=command>
pwd && ls
</parameter>
</function>

USER: EXECUTION RESULT of [execute_bash]:
/workspace
openhands@runtime:~/workspace$
""",
        'run_server': """
ASSISTANT:
Let me run the Python file for you:
<function=execute_bash>
<parameter=command>
python3 app.py > server.log 2>&1 &
</parameter>
</function>

USER: EXECUTION RESULT of [execute_bash]:
[1] 121
[1]+  Exit 1                  python3 app.py > server.log 2>&1

ASSISTANT:
Looks like the server was running with PID 121 then crashed. Let me check the server log:
<function=execute_bash>
<parameter=command>
cat server.log
</parameter>
</function>

USER: EXECUTION RESULT of [execute_bash]:
Traceback (most recent call last):
  File "/workspace/app.py", line 2, in <module>
    from flask import Flask
ModuleNotFoundError: No module named 'flask'

ASSISTANT:
Looks like the server crashed because the `flask` module is not installed. Let me install the `flask` module for you:
<function=execute_bash>
<parameter=command>
pip3 install flask
</parameter>
</function>

USER: EXECUTION RESULT of [execute_bash]:
Defaulting to user installation because normal site-packages is not writeable
Collecting flask
  Using cached flask-3.0.3-py3-none-any.whl (101 kB)
Collecting blinker>=1.6.2
  Using cached blinker-1.7.0-py3-none-any.whl (13 kB)
Collecting Werkzeug>=3.0.0
  Using cached werkzeug-3.0.2-py3-none-any.whl (226 kB)
Collecting click>=8.1.3
  Using cached click-8.1.7-py3-none-any.whl (97 kB)
Collecting itsdangerous>=2.1.2
  Using cached itsdangerous-2.2.0-py3-none-any.whl (16 kB)
Requirement already satisfied: Jinja2>=3.1.2 in /home/openhands/.local/lib/python3.10/site-packages (from flask) (3.1.3)
Requirement already satisfied: MarkupSafe>=2.0 in /home/openhands/.local/lib/python3.10/site-packages (from Jinja2>=3.1.2->flask) (2.1.5)
Installing collected packages: Werkzeug, itsdangerous, click, blinker, flask
Successfully installed Werkzeug-3.0.2 blinker-1.7.0 click-8.1.7 flask-3.0.3 itsdangerous-2.2.0

ASSISTANT:
The `flask` module is installed successfully. Let me run the Python file again:
<function=execute_bash>
<parameter=command>
python3 app.py > server.log 2>&1 &
</parameter>
</function>

USER: EXECUTION RESULT of [execute_bash]:
[1] 124

ASSISTANT:
Let me check the server log again:
<function=execute_bash>
<parameter=command>
cat server.log
</parameter>
</function>

USER: EXECUTION RESULT of [execute_bash]:
* Serving Flask app 'app'
 * Debug mode: off
WARNING: This is a development server. Do not use it in a production deployment. Use a production WSGI server instead.
 * Running on http://127.0.0.1:5000
Press CTRL+C to quit

ASSISTANT:
The server is running on port 5000 with PID 124. You can access the list of numbers by visiting http://127.0.0.1:5000. If you have any further questions, feel free to ask!
""",
        'kill_server': """
USER: Now kill the server, make it display the numbers in a table format.

ASSISTANT:
Sure! Let me stop the server first:
<function=execute_bash>
<parameter=command>
kill 124
</parameter>
</function>

USER: EXECUTION RESULT of [execute_bash]:
[1]+  Terminated              python3 app.py > server.log 2>&1
""",
        'run_server_again': """
ASSISTANT:
Running the updated file:
<function=execute_bash>
<parameter=command>
python3 app.py > server.log 2>&1 &
</parameter>
</function>

USER: EXECUTION RESULT of [execute_bash]:
[1] 126

ASSISTANT:
The server is running on port 5000 with PID 126. You can access the list of numbers in a table format by visiting http://127.0.0.1:5000.
""",
    },
    'str_replace_editor': {
        'create_file': """
ASSISTANT:
There is no `app.py` file in the current directory. Let me create a Python file `app.py`:
<function=str_replace_editor>
<parameter=command>create</parameter>
<parameter=path>/workspace/app.py</parameter>
<parameter=file_text>
from flask import Flask
app = Flask(__name__)

@app.route('/')
def index():
    numbers = list(range(1, 11))
    return str(numbers)

if __name__ == '__main__':
    app.run(port=5000)
</parameter>
</function>

USER: EXECUTION RESULT of [str_replace_editor]:
File created successfully at: /workspace/app.py
""",
        'edit_file': """
ASSISTANT:
Now let me display the numbers in a table format:
<function=str_replace_editor>
<parameter=command>str_replace</parameter>
<parameter=path>/workspace/app.py</parameter>
<parameter=old_str>return str(numbers)</parameter>
<parameter=new_str>return '<table>' + ''.join([f'<tr><td>{i}</td></tr>' for i in numbers]) + '</table>'</parameter>
</function>

USER: EXECUTION RESULT of [str_replace_editor]:
The file /workspace/app.py has been edited. Here's the result of running `cat -n` on a snippet of /workspace/app.py:
     3
     4  @app.route('/')
     5  def index():
     6      numbers = list(range(1, 11))
     7      return '<table>' + ''.join([f'<tr><td>{i}</td></tr>' for i in numbers]) + '</table>'
     8
     9  if __name__ == '__main__':
    10      app.run(port=5000)
Review the changes and make sure they are as expected. Edit the file again if necessary.

""",
    },
    'browser': {
        'view_page': """
ASSISTANT:
Let me check how the page looks in the browser:
<function=browser>
<parameter=code>
goto('http://127.0.0.1:5000')
noop(1000)  # Wait for page to load
</parameter>
</function>

USER: EXECUTION RESULT of [browser]:
[Browser shows the numbers in a table format]
"""
    },
    'finish': {
        'task_completed': """
ASSISTANT:
The server is running on port 5000 with PID 126. You can access the list of numbers in a table format by visiting http://127.0.0.1:5000. Let me know if you have any further requests!
<function=finish>
<parameter=message>The task has been completed. The web server is running and displaying numbers 1-10 in a table format at http://127.0.0.1:5000.</parameter>
<parameter=task_completed>true</parameter>
</function>
"""
    },
}


def get_example_for_tools(tools: list[dict]) -> str:
    """Generate an in-context learning example based on available tools."""
    available_tools = set()
    for tool in tools:
        if tool['type'] == 'function':
            name = tool['function']['name']
            if name == EXECUTE_BASH_TOOL_NAME:
                available_tools.add('execute_bash')
            elif name == STR_REPLACE_EDITOR_TOOL_NAME:
                available_tools.add('str_replace_editor')
            elif name == BROWSER_TOOL_NAME:
                available_tools.add('browser')
            elif name == FINISH_TOOL_NAME:
                available_tools.add('finish')

    if not available_tools:
        return ''

    example = """Here's a running example of how to perform a task with the provided tools.

--------------------- START OF EXAMPLE ---------------------

USER: Create a list of numbers from 1 to 10, and display them in a web page at port 5000.

"""

    # Build example based on available tools
    if 'execute_bash' in available_tools:
        example += TOOL_EXAMPLES['execute_bash']['check_dir']

    if 'str_replace_editor' in available_tools:
        example += TOOL_EXAMPLES['str_replace_editor']['create_file']

    if 'execute_bash' in available_tools:
        example += TOOL_EXAMPLES['execute_bash']['run_server']

    if 'browser' in available_tools:
        example += TOOL_EXAMPLES['browser']['view_page']

    if 'execute_bash' in available_tools:
        example += TOOL_EXAMPLES['execute_bash']['kill_server']

    if 'str_replace_editor' in available_tools:
        example += TOOL_EXAMPLES['str_replace_editor']['edit_file']

    if 'execute_bash' in available_tools:
        example += TOOL_EXAMPLES['execute_bash']['run_server_again']

    if 'finish' in available_tools:
        example += TOOL_EXAMPLES['finish']['task_completed']

    example += """
--------------------- END OF EXAMPLE ---------------------

Do NOT assume the environment is the same as in the example above.

--------------------- NEW TASK DESCRIPTION ---------------------
"""
    example = example.lstrip()

    return example


IN_CONTEXT_LEARNING_EXAMPLE_PREFIX = get_example_for_tools

IN_CONTEXT_LEARNING_EXAMPLE_SUFFIX = """
--------------------- END OF NEW TASK DESCRIPTION ---------------------

PLEASE follow the format strictly! PLEASE EMIT ONE AND ONLY ONE FUNCTION CALL PER MESSAGE.
"""

# Regex patterns for function call parsing
FN_REGEX_PATTERN = r'<function=([^>]+)>\n(.*?)</function>'
FN_PARAM_REGEX_PATTERN = r'<parameter=([^>]+)>(.*?)</parameter>'

# Add new regex pattern for tool execution results
TOOL_RESULT_REGEX_PATTERN = r'EXECUTION RESULT of \[(.*?)\]:\n(.*)'


def convert_tool_call_to_string(tool_call: dict) -> str:
    """Convert tool call to content in string format."""
    if 'function' not in tool_call:
        raise FunctionCallConversionError("Tool call must contain 'function' key.")
    if 'id' not in tool_call:
        raise FunctionCallConversionError("Tool call must contain 'id' key.")
    if 'type' not in tool_call:
        raise FunctionCallConversionError("Tool call must contain 'type' key.")
    if tool_call['type'] != 'function':
        raise FunctionCallConversionError("Tool call type must be 'function'.")

    ret = f'<function={tool_call["function"]["name"]}>\n'
    try:
        args = json.loads(tool_call['function']['arguments'])
    except json.JSONDecodeError as e:
        raise FunctionCallConversionError(
            f'Failed to parse arguments as JSON. Arguments: {tool_call["function"]["arguments"]}'
        ) from e
    for param_name, param_value in args.items():
        is_multiline = isinstance(param_value, str) and '\n' in param_value
        ret += f'<parameter={param_name}>'
        if is_multiline:
            ret += '\n'
        ret += f'{param_value}'
        if is_multiline:
            ret += '\n'
        ret += '</parameter>\n'
    ret += '</function>'
    return ret


def convert_tools_to_description(tools: list[dict]) -> str:
    ret = ''
    for i, tool in enumerate(tools):
        assert tool['type'] == 'function'
        fn = tool['function']
        if i > 0:
            ret += '\n'
        ret += f'---- BEGIN FUNCTION #{i + 1}: {fn["name"]} ----\n'
        ret += f'Description: {fn["description"]}\n'

        if 'parameters' in fn:
            ret += 'Parameters:\n'
            properties = fn['parameters'].get('properties', {})
            required_params = set(fn['parameters'].get('required', []))

            for j, (param_name, param_info) in enumerate(properties.items()):
                # Indicate required/optional in parentheses with type
                is_required = param_name in required_params
                param_status = 'required' if is_required else 'optional'
                param_type = param_info.get('type', 'string')

                # Get parameter description
                desc = param_info.get('description', 'No description provided')

                # Handle enum values if present
                if 'enum' in param_info:
                    enum_values = ', '.join(f'`{v}`' for v in param_info['enum'])
                    desc += f'\nAllowed values: [{enum_values}]'

                ret += (
                    f'  ({j + 1}) {param_name} ({param_type}, {param_status}): {desc}\n'
                )
        else:
            ret += 'No parameters are required for this function.\n'

        ret += f'---- END FUNCTION #{i + 1} ----\n'
    return ret


def convert_fncall_messages_to_non_fncall_messages(
    messages: list[dict],
    tools: list[ChatCompletionToolParam],
    add_in_context_learning_example: bool = True,
) -> list[dict]:
    """Convert function calling messages to non-function calling messages."""
    messages = copy.deepcopy(messages)

    formatted_tools = convert_tools_to_description(tools)
    system_prompt_suffix = SYSTEM_PROMPT_SUFFIX_TEMPLATE.format(
        description=formatted_tools
    )

    converted_messages = []
    first_user_message_encountered = False
    for message in messages:
        role = message['role']
        content = message['content']

        # 1. SYSTEM MESSAGES
        # append system prompt suffix to content
        if role == 'system':
            if isinstance(content, str):
                content += system_prompt_suffix
            elif isinstance(content, list):
                if content and content[-1]['type'] == 'text':
                    content[-1]['text'] += system_prompt_suffix
                else:
                    content.append({'type': 'text', 'text': system_prompt_suffix})
            else:
                raise FunctionCallConversionError(
                    f'Unexpected content type {type(content)}. Expected str or list. Content: {content}'
                )
            converted_messages.append({'role': 'system', 'content': content})

        # 2. USER MESSAGES (no change)
        elif role == 'user':
            # Add in-context learning example for the first user message
            if not first_user_message_encountered and add_in_context_learning_example:
                first_user_message_encountered = True

                # Generate example based on available tools
                example = IN_CONTEXT_LEARNING_EXAMPLE_PREFIX(tools)

                # Add example if we have any tools
                if example:
                    # add in-context learning example
                    if isinstance(content, str):
                        content = example + content + IN_CONTEXT_LEARNING_EXAMPLE_SUFFIX
                    elif isinstance(content, list):
                        if content and content[0]['type'] == 'text':
                            content[0]['text'] = (
                                example
                                + content[0]['text']
                                + IN_CONTEXT_LEARNING_EXAMPLE_SUFFIX
                            )
                        else:
                            content = (
                                [
                                    {
                                        'type': 'text',
                                        'text': example,
                                    }
                                ]
                                + content
                                + [
                                    {
                                        'type': 'text',
                                        'text': IN_CONTEXT_LEARNING_EXAMPLE_SUFFIX,
                                    }
                                ]
                            )
                    else:
                        raise FunctionCallConversionError(
                            f'Unexpected content type {type(content)}. Expected str or list. Content: {content}'
                        )
            converted_messages.append(
                {
                    'role': 'user',
                    'content': content,
                }
            )

        # 3. ASSISTANT MESSAGES
        # - 3.1 no change if no function call
        # - 3.2 change if function call
        elif role == 'assistant':
            if 'tool_calls' in message and message['tool_calls'] is not None:
                if len(message['tool_calls']) != 1:
                    raise FunctionCallConversionError(
                        f'Expected exactly one tool call in the message. More than one tool call is not supported. But got {len(message["tool_calls"])} tool calls. Content: {content}'
                    )
                try:
                    tool_content = convert_tool_call_to_string(message['tool_calls'][0])
                except FunctionCallConversionError as e:
                    raise FunctionCallConversionError(
                        f'Failed to convert tool call to string.\nCurrent tool call: {message["tool_calls"][0]}.\nRaw messages: {json.dumps(messages, indent=2)}'
                    ) from e
                if isinstance(content, str):
                    content += '\n\n' + tool_content
                    content = content.lstrip()
                elif isinstance(content, list):
                    if content and content[-1]['type'] == 'text':
                        content[-1]['text'] += '\n\n' + tool_content
                        content[-1]['text'] = content[-1]['text'].lstrip()
                    else:
                        content.append({'type': 'text', 'text': tool_content})
                else:
                    raise FunctionCallConversionError(
                        f'Unexpected content type {type(content)}. Expected str or list. Content: {content}'
                    )
            converted_messages.append({'role': 'assistant', 'content': content})

        # 4. TOOL MESSAGES (tool outputs)
        elif role == 'tool':
            # Convert tool result as user message
            tool_name = message.get('name', 'function')
            prefix = f'EXECUTION RESULT of [{tool_name}]:\n'
            # and omit "tool_call_id" AND "name"
            if isinstance(content, str):
                content = prefix + content
            elif isinstance(content, list):
                if content and (
                    first_text_content := next(
                        (c for c in content if c['type'] == 'text'), None
                    )
                ):
                    first_text_content['text'] = prefix + first_text_content['text']
                else:
                    content = [{'type': 'text', 'text': prefix}] + content
            else:
                raise FunctionCallConversionError(
                    f'Unexpected content type {type(content)}. Expected str or list. Content: {content}'
                )
            if 'cache_control' in message:
                content[-1]['cache_control'] = {'type': 'ephemeral'}
            converted_messages.append({'role': 'user', 'content': content})
        else:
            raise FunctionCallConversionError(
                f'Unexpected role {role}. Expected system, user, assistant or tool.'
            )
    return converted_messages


def _extract_and_validate_params(
    matching_tool: dict, param_matches: Iterable[re.Match], fn_name: str
) -> dict:
    params = {}
    # Parse and validate parameters
    required_params = set()
    if 'parameters' in matching_tool and 'required' in matching_tool['parameters']:
        required_params = set(matching_tool['parameters'].get('required', []))

    allowed_params = set()
    if 'parameters' in matching_tool and 'properties' in matching_tool['parameters']:
        allowed_params = set(matching_tool['parameters']['properties'].keys())

    param_name_to_type = {}
    if 'parameters' in matching_tool and 'properties' in matching_tool['parameters']:
        param_name_to_type = {
            name: val.get('type', 'string')
            for name, val in matching_tool['parameters']['properties'].items()
        }

    # Collect parameters
    found_params = set()
    for param_match in param_matches:
        param_name = param_match.group(1)
        param_value = param_match.group(2)

        # Validate parameter is allowed
        if allowed_params and param_name not in allowed_params:
            raise FunctionCallValidationError(
                f"Parameter '{param_name}' is not allowed for function '{fn_name}'. "
                f'Allowed parameters: {allowed_params}'
            )

        # Validate and convert parameter type
        # supported: string, integer, array
        if param_name in param_name_to_type:
            if param_name_to_type[param_name] == 'integer':
                try:
                    param_value = int(param_value)
                except ValueError:
                    raise FunctionCallValidationError(
                        f"Parameter '{param_name}' is expected to be an integer."
                    )
            elif param_name_to_type[param_name] == 'array':
                try:
                    param_value = json.loads(param_value)
                except json.JSONDecodeError:
                    raise FunctionCallValidationError(
                        f"Parameter '{param_name}' is expected to be an array."
                    )
            else:
                # string
                pass

        # Enum check
        if 'enum' in matching_tool['parameters']['properties'][param_name]:
            if (
                param_value
                not in matching_tool['parameters']['properties'][param_name]['enum']
            ):
                raise FunctionCallValidationError(
                    f"Parameter '{param_name}' is expected to be one of {matching_tool['parameters']['properties'][param_name]['enum']}."
                )

        params[param_name] = param_value
        found_params.add(param_name)

    # Check all required parameters are present
    missing_params = required_params - found_params
    if missing_params:
        raise FunctionCallValidationError(
            f"Missing required parameters for function '{fn_name}': {missing_params}"
        )
    return params


def _fix_stopword(content: str) -> str:
    """Fix the issue when some LLM would NOT return the stopword."""
    if '<function=' in content and content.count('<function=') == 1:
        if content.endswith('</'):
            content = content.rstrip() + 'function>'
        else:
            content = content + '\n</function>'
    return content


def convert_non_fncall_messages_to_fncall_messages(
    messages: list[dict],
    tools: list[ChatCompletionToolParam],
) -> list[dict]:
    """Convert non-function calling messages back to function calling messages."""
    messages = copy.deepcopy(messages)
    formatted_tools = convert_tools_to_description(tools)
    system_prompt_suffix = SYSTEM_PROMPT_SUFFIX_TEMPLATE.format(
        description=formatted_tools
    )

    converted_messages = []
    tool_call_counter = 1  # Counter for tool calls

    first_user_message_encountered = False
    for message in messages:
        role, content = message['role'], message['content']
        content = content or ''  # handle cases where content is None
        # For system messages, remove the added suffix
        if role == 'system':
            if isinstance(content, str):
                # Remove the suffix if present
                content = content.split(system_prompt_suffix)[0]
            elif isinstance(content, list):
                if content and content[-1]['type'] == 'text':
                    # Remove the suffix from the last text item
                    content[-1]['text'] = content[-1]['text'].split(
                        system_prompt_suffix
                    )[0]
            converted_messages.append({'role': 'system', 'content': content})
        # Skip user messages (no conversion needed)
        elif role == 'user':
            # Check & replace in-context learning example
            if not first_user_message_encountered:
                first_user_message_encountered = True
                if isinstance(content, str):
                    # Remove any existing example
                    if content.startswith(IN_CONTEXT_LEARNING_EXAMPLE_PREFIX(tools)):
                        content = content.replace(
                            IN_CONTEXT_LEARNING_EXAMPLE_PREFIX(tools), '', 1
                        )
                    if content.endswith(IN_CONTEXT_LEARNING_EXAMPLE_SUFFIX):
                        content = content.replace(
                            IN_CONTEXT_LEARNING_EXAMPLE_SUFFIX, '', 1
                        )
                elif isinstance(content, list):
                    for item in content:
                        if item['type'] == 'text':
                            # Remove any existing example
                            example = IN_CONTEXT_LEARNING_EXAMPLE_PREFIX(tools)
                            if item['text'].startswith(example):
                                item['text'] = item['text'].replace(example, '', 1)
                            if item['text'].endswith(
                                IN_CONTEXT_LEARNING_EXAMPLE_SUFFIX
                            ):
                                item['text'] = item['text'].replace(
                                    IN_CONTEXT_LEARNING_EXAMPLE_SUFFIX, '', 1
                                )
                else:
                    raise FunctionCallConversionError(
                        f'Unexpected content type {type(content)}. Expected str or list. Content: {content}'
                    )

            # Check for tool execution result pattern
            if isinstance(content, str):
                tool_result_match = re.search(
                    TOOL_RESULT_REGEX_PATTERN, content, re.DOTALL
                )
            elif isinstance(content, list):
                tool_result_match = next(
                    (
                        _match
                        for item in content
                        if item.get('type') == 'text'
                        and (
                            _match := re.search(
                                TOOL_RESULT_REGEX_PATTERN, item['text'], re.DOTALL
                            )
                        )
                    ),
                    None,
                )
            else:
                raise FunctionCallConversionError(
                    f'Unexpected content type {type(content)}. Expected str or list. Content: {content}'
                )

            if tool_result_match:
                if not (
                    isinstance(content, str)
                    or (
                        isinstance(content, list)
                        and len(content) == 1
                        and content[0].get('type') == 'text'
                    )
                ):
                    raise FunctionCallConversionError(
                        f'Expected str or list with one text item when tool result is present in the message. Content: {content}'
                    )
                tool_name = tool_result_match.group(1)
                tool_result = tool_result_match.group(2).strip()

                # Convert to tool message format
                converted_messages.append(
                    {
                        'role': 'tool',
                        'name': tool_name,
                        'content': [{'type': 'text', 'text': tool_result}]
                        if isinstance(content, list)
                        else tool_result,
                        'tool_call_id': f'toolu_{tool_call_counter - 1:02d}',  # Use last generated ID
                    }
                )
            else:
                converted_messages.append({'role': 'user', 'content': content})

        # Handle assistant messages
        elif role == 'assistant':
            if isinstance(content, str):
                content = _fix_stopword(content)
                fn_match = re.search(FN_REGEX_PATTERN, content, re.DOTALL)
            elif isinstance(content, list):
                if content and content[-1]['type'] == 'text':
                    content[-1]['text'] = _fix_stopword(content[-1]['text'])
                    fn_match = re.search(
                        FN_REGEX_PATTERN, content[-1]['text'], re.DOTALL
                    )
                else:
                    fn_match = None
                fn_match_exists = any(
                    item.get('type') == 'text'
                    and re.search(FN_REGEX_PATTERN, item['text'], re.DOTALL)
                    for item in content
                )
                if fn_match_exists and not fn_match:
                    raise FunctionCallConversionError(
                        f'Expecting function call in the LAST index of content list. But got content={content}'
                    )
            else:
                raise FunctionCallConversionError(
                    f'Unexpected content type {type(content)}. Expected str or list. Content: {content}'
                )

            if fn_match:
                fn_name = fn_match.group(1)
                fn_body = fn_match.group(2)
                matching_tool = next(
                    (
                        tool['function']
                        for tool in tools
                        if tool['type'] == 'function'
                        and tool['function']['name'] == fn_name
                    ),
                    None,
                )
                # Validate function exists in tools
                if not matching_tool:
                    raise FunctionCallValidationError(
                        f"Function '{fn_name}' not found in available tools: {[tool['function']['name'] for tool in tools if tool['type'] == 'function']}"
                    )

                # Parse parameters
                param_matches = re.finditer(FN_PARAM_REGEX_PATTERN, fn_body, re.DOTALL)
                params = _extract_and_validate_params(
                    matching_tool, param_matches, fn_name
                )

                # Create tool call with unique ID
                tool_call_id = f'toolu_{tool_call_counter:02d}'
                tool_call = {
                    'index': 1,  # always 1 because we only support **one tool call per message**
                    'id': tool_call_id,
                    'type': 'function',
                    'function': {'name': fn_name, 'arguments': json.dumps(params)},
                }
                tool_call_counter += 1  # Increment counter

                # Remove the function call part from content
                if isinstance(content, list):
                    assert content and content[-1]['type'] == 'text'
                    content[-1]['text'] = (
                        content[-1]['text'].split('<function=')[0].strip()
                    )
                elif isinstance(content, str):
                    content = content.split('<function=')[0].strip()
                else:
                    raise FunctionCallConversionError(
                        f'Unexpected content type {type(content)}. Expected str or list. Content: {content}'
                    )

                converted_messages.append(
                    {'role': 'assistant', 'content': content, 'tool_calls': [tool_call]}
                )
            else:
                # No function call, keep message as is
                converted_messages.append(message)

        else:
            raise FunctionCallConversionError(
                f'Unexpected role {role}. Expected system, user, or assistant in non-function calling messages.'
            )
    return converted_messages


def convert_from_multiple_tool_calls_to_single_tool_call_messages(
    messages: list[dict],
    ignore_final_tool_result: bool = False,
) -> list[dict]:
    """Break one message with multiple tool calls into multiple messages."""
    converted_messages = []

    pending_tool_calls: dict[str, dict] = {}
    for message in messages:
        role, content = message['role'], message['content']
        if role == 'assistant':
            if message.get('tool_calls') and len(message['tool_calls']) > 1:
                # handle multiple tool calls by breaking them into multiple messages
                for i, tool_call in enumerate(message['tool_calls']):
                    pending_tool_calls[tool_call['id']] = {
                        'role': 'assistant',
                        'content': content if i == 0 else '',
                        'tool_calls': [tool_call],
                    }
            else:
                converted_messages.append(message)
        elif role == 'tool':
            if message['tool_call_id'] in pending_tool_calls:
                # remove the tool call from the pending list
                _tool_call_message = pending_tool_calls.pop(message['tool_call_id'])
                converted_messages.append(_tool_call_message)
                # add the tool result
                converted_messages.append(message)
            else:
                assert len(pending_tool_calls) == 0, (
                    f'Found pending tool calls but not found in pending list: {pending_tool_calls=}'
                )
                converted_messages.append(message)
        else:
            assert len(pending_tool_calls) == 0, (
                f'Found pending tool calls but not expect to handle it with role {role}: {pending_tool_calls=}, {message=}'
            )
            converted_messages.append(message)

    if not ignore_final_tool_result and len(pending_tool_calls) > 0:
        raise FunctionCallConversionError(
            f'Found pending tool calls but no tool result: {pending_tool_calls=}'
        )
    return converted_messages