Checklist

• 1. I have searched related issues but cannot get the expected help.
• 2. The bug has not been fixed in the latest version.
• 3. Please note that if the bug-related issue you submitted lacks corresponding environment info and a minimal reproducible demo, it will be challenging for us to reproduce and resolve the issue, reducing the likelihood of receiving feedback.
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Describe the bug

1. Discrepancy in chat_template for tool_calls:
   A comparison between SGLang's DeepSeekV3 chat_template and Hugging Face's chat_template reveals an additional tojson applied to tool['function']['arguments'] in SGLang's implementation:
   Sglang(./examples/chat_template/tool_chat_template_deepseekv31.jinja):
   {{'<｜tool▁call▁begin｜>'+ tool['function']['name'] + '<｜tool▁sep｜>' + tool['function']['arguments']|tojson + '<｜tool▁call▁end｜>'}}.
   HuggingFace：
   {{'<｜tool▁call▁begin｜>'+ tool['function']['name'] + '<｜tool▁sep｜>' + tool['function']['arguments'] + '<｜tool▁call▁end｜>'}}

2. Impact on Multi-Round FunctionCall (BFCL_V3 Evaluation):
   The extra tojson call causes double-escaping of function arguments, leading to incorrect tool_calls and abnormal FunctionCall scores in multi-round BFCL_V3 evaluations.
   Abnormal Output Example：
   normal_text="Now I'll get the current stock information for Zeta Corp (symbol: ZETA):" calls=[ToolCallItem(tool_index=-1, name='get_stock_info', parameters='"{\\"symbol\\": \\"ZETA\\"}"')]
   Normal Output Example：
   normal_text="I'll retrieve comprehensive information about NVIDIA (NVDA) stock for you." calls=[ToolCallItem(tool_index=-1, name='get_stock_info', parameters='{"symbol": "NVDA"}')]

3. Proposed Solution/Recommendation:
   It is recommended to refer to other models, such as kimi, and add an arguments type judgment：
   <|tool_call_begin|>{{ formatted_id }}<|tool_call_argument_begin|>{% if tool_call['function']['arguments'] is string %}{{ tool_call['function']['arguments'] }}{% else %}{{ tool_call['function']['arguments'] | tojson }}{% endif %}<|tool_call_end|>

Reproduction

Model：DeepSeekV3 & V31 & V32
Dataset：BFCL_V3 Multi-round FunctionCall

python3 -m sglang.launch_server
--model deepseek-ai/DeepSeek-V3.1
--tp 8
--port 30000
--host 0.0.0.0
--mem-fraction-static 0.9
--tool-call-parser deepseekv31
--chat-template ./examples/chat_template/tool_chat_template_deepseekv31.jinja

Environment

H20 + SGlang 053