How to achieve reliable native function calling
#9
by
Ithanil
- opened
I had found the native function calling with the default chat template extremely unreliable, because the model (at least in FP8) would frequently omit the initial tag on tool calls, especially when the tool call was attempted after a textual response. I tried a lot of variations to the function calling instructions in the chat template, until I arrived at something that actually works reliably:
Function calls HAVE to be enclosed within <tool_call> and </tool_call> tags. If you choose to call a function ONLY reply in the following format with NO suffix:
<tool_call>
<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>
</tool_call>
<IMPORTANT>
Reminder:
- Function calls MUST follow the specified format: an inner <function=...></function> block must be nested within <tool_call></tool_call> XML tags
- Do NOT omit the initial <tool_call> tag
- Required parameters MUST be specified
- 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>
The full chat template, with above instructions inserted into Unsloth's fixed chat template, is as follows:
{#- Copyright 2025-present the Unsloth team. All rights reserved. #}
{#- Copyright 2025 Jan Kessler. All rights reserved. #}
{#- Licensed under the Apache License, Version 2.0 (the "License") #}
{#- Edits made by Unsloth to fix the chat template, tool calling instructions improved by Jan Kessler #}
{% macro render_item_list(item_list, tag_name='required') %}
{%- if item_list is defined and item_list is iterable and item_list | length > 0 %}
{%- if tag_name %}{{- '\n<' ~ tag_name ~ '>' -}}{% endif %}
{{- '[' }}
{%- for item in item_list -%}
{%- if loop.index > 1 %}{{- ", "}}{% endif -%}
{%- if item is string -%}
{{ "`" ~ item ~ "`" }}
{%- else -%}
{{ item }}
{%- endif -%}
{%- endfor -%}
{{- ']' }}
{%- if tag_name %}{{- '</' ~ tag_name ~ '>' -}}{% endif %}
{%- endif %}
{% endmacro %}
{%- if messages[0]["role"] == "system" %}
{%- set system_message = messages[0]["content"] %}
{%- set loop_messages = messages[1:] %}
{%- else %}
{%- set loop_messages = messages %}
{%- endif %}
{%- if not tools is defined %}
{%- set tools = [] %}
{%- endif %}
{%- if system_message is defined %}
{{- "<|im_start|>system\n" + system_message }}
{%- else %}
{%- if tools is iterable and tools | length > 0 %}
{{- "<|im_start|>system\nYou are Qwen, a helpful AI assistant that can interact with a computer to solve tasks." }}
{%- endif %}
{%- endif %}
{%- if tools is iterable and tools | length > 0 %}
{{- "\n\nYou have access to the following functions:\n\n" }}
{{- "<tools>" }}
{%- for tool in tools %}
{%- if tool.function is defined %}
{%- set tool = tool.function %}
{%- endif %}
{{- "\n<function>\n<name>" ~ tool.name ~ "</name>" }}
{{- '\n<description>' ~ (tool.description | trim) ~ '</description>' }}
{{- '\n<parameters>' }}
{%- for param_name, param_fields in tool.parameters.properties|items %}
{{- '\n<parameter>' }}
{{- '\n<name>' ~ param_name ~ '</name>' }}
{%- if param_fields.type is defined %}
{{- '\n<type>' ~ (param_fields.type | string) ~ '</type>' }}
{%- endif %}
{%- if param_fields.description is defined %}
{{- '\n<description>' ~ (param_fields.description | trim) ~ '</description>' }}
{%- endif %}
{{- render_item_list(param_fields.enum, 'enum') }}
{%- set handled_keys = ['type', 'description', 'enum', 'required'] %}
{%- for json_key in param_fields %}
{%- if json_key not in handled_keys %}
{%- set normed_json_key = json_key | replace("-", "_") | replace(" ", "_") | replace("$", "") %}
{%- if param_fields[json_key] is mapping %}
{{- '\n<' ~ normed_json_key ~ '>' ~ (param_fields[json_key] | tojson | safe) ~ '</' ~ normed_json_key ~ '>' }}
{%- else %}
{{- '\n<' ~ normed_json_key ~ '>' ~ (param_fields[json_key] | string) ~ '</' ~ normed_json_key ~ '>' }}
{%- endif %}
{%- endif %}
{%- endfor %}
{{- render_item_list(param_fields.required, 'required') }}
{{- '\n</parameter>' }}
{%- endfor %}
{{- render_item_list(tool.parameters.required, 'required') }}
{{- '\n</parameters>' }}
{%- if tool.return is defined %}
{%- if tool.return is mapping %}
{{- '\n<return>' ~ (tool.return | tojson | safe) ~ '</return>' }}
{%- else %}
{{- '\n<return>' ~ (tool.return | string) ~ '</return>' }}
{%- endif %}
{%- endif %}
{{- '\n</function>' }}
{%- endfor %}
{{- "\n</tools>" }}
{{- '\n\nFunction calls HAVE to be enclosed within <tool_call> and </tool_call> tags. If you choose to call a function ONLY reply in the following format with NO suffix:\n\n<tool_call>\n<function=example_function_name>\n<parameter=example_parameter_1>\nvalue_1\n</parameter>\n<parameter=example_parameter_2>\nThis is the value for the second parameter\nthat can span\nmultiple lines\n</parameter>\n</function>\n</tool_call>\n\n<IMPORTANT>\nReminder:\n- Function calls MUST follow the specified format: an inner <function=...></function> block must be nested within <tool_call></tool_call> XML tags\n- Do NOT omit the initial <tool_call> tag\n- Required parameters MUST be specified\n- You may provide optional reasoning for your function call in natural language BEFORE the function call, but NOT after\n- 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\n</IMPORTANT>' }}
{%- endif %}
{%- if system_message is defined %}
{{- '<|im_end|>\n' }}
{%- else %}
{%- if tools is iterable and tools | length > 0 %}
{{- '<|im_end|>\n' }}
{%- endif %}
{%- endif %}
{%- for message in loop_messages %}
{%- if message.role == "assistant" and message.tool_calls is defined and message.tool_calls is iterable and message.tool_calls | length > 0 %}
{{- '<|im_start|>' + message.role }}
{%- if message.content is defined and message.content is string and message.content | trim | length > 0 %}
{{- '\n' + message.content | trim + '\n' }}
{%- endif %}
{%- for tool_call in message.tool_calls %}
{%- if tool_call.function is defined %}
{%- set tool_call = tool_call.function %}
{%- endif %}
{{- '\n<tool_call>\n<function=' + tool_call.name + '>\n' }}
{%- if tool_call.arguments is defined %}
{%- for args_name, args_value in tool_call.arguments|items %}
{{- '<parameter=' + args_name + '>\n' }}
{%- set args_value = args_value if args_value is string else args_value | string %}
{{- args_value }}
{{- '\n</parameter>\n' }}
{%- endfor %}
{%- endif %}
{{- '</function>\n</tool_call>' }}
{%- endfor %}
{{- '<|im_end|>\n' }}
{%- elif message.role == "user" or message.role == "system" or message.role == "assistant" %}
{{- '<|im_start|>' + message.role + '\n' + message.content + '<|im_end|>' + '\n' }}
{%- elif message.role == "tool" %}
{%- if loop.previtem and loop.previtem.role != "tool" %}
{{- '<|im_start|>user\n' }}
{%- endif %}
{{- '<tool_response>\n' }}
{{- message.content }}
{{- '\n</tool_response>\n' }}
{%- if not loop.last and loop.nextitem.role != "tool" %}
{{- '<|im_end|>\n' }}
{%- elif loop.last %}
{{- '<|im_end|>\n' }}
{%- endif %}
{%- else %}
{{- '<|im_start|>' + message.role + '\n' + message.content + '<|im_end|>\n' }}
{%- endif %}
{%- endfor %}
{%- if add_generation_prompt %}
{{- '<|im_start|>assistant\n' }}
{%- endif %}
{#- Copyright 2025-present the Unsloth team. All rights reserved. #}
{#- Licensed under the Apache License, Version 2.0 (the "License") #}