Custom OpenAI-compatible providers don't send tools parameter for function calling

Summary

OpenClaw doesn't send the tools parameter to custom OpenAI-compatible API providers (e.g., SiliconFlow, together.ai) even when those providers fully support function calling according to OpenAI API spec. This prevents tool execution on otherwise compatible models.

Environment

• OpenClaw Version: 2026.2.2-3
• Provider: SiliconFlow (custom openai-completions provider)
• Model: deepseek-ai/DeepSeek-V3
• Configuration Type: Custom provider with "api": "openai-completions"

Expected Behavior

When using a custom OpenAI-compatible provider that supports function calling:

1. OpenClaw should send the tools parameter in API requests
2. The model should receive tool definitions and return tool_calls in responses
3. OpenClaw should execute the requested tools

Actual Behavior

1. OpenClaw does NOT send the tools parameter to custom providers
2. Models output JSON text instead of structured tool_calls
3. Tools are never executed

Configuration Used

{
  "models": {
    "providers": {
      "siliconflow": {
        "baseUrl": "https://api.siliconflow.cn/v1",
        "apiKey": "sk-***",
        "api": "openai-completions",
        "models": [
          {
            "id": "deepseek-ai/DeepSeek-V3",
            "name": "DeepSeek V3",
            "reasoning": false,
            "contextWindow": 65536,
            "maxTokens": 8192
          }
        ]
      }
    }
  },
  "agents": {
    "defaults": {
      "model": {
        "primary": "siliconflow/deepseek-ai/DeepSeek-V3"
      }
    }
  },
  "tools": {
    "web": {
      "search": {
        "apiKey": "BSA***"
      }
    }
  }
}

Steps to Reproduce

1. Configure a custom OpenAI-compatible provider (SiliconFlow, together.ai, etc.)
2. Enable web_search tool with valid Brave API key
3. Ask the agent to search for information: "查询理想汽车股价"
4. Observe that the model outputs JSON text like {"name": "web_search", "arguments": {...}} instead of executing the tool

Verification That Provider Supports Function Calling

Direct API test proves the provider DOES support function calling:

curl https://api.siliconflow.cn/v1/chat/completions \
  -H "Content-Type: application/json" \
  -H "Authorization: Bearer sk-***" \
  -d '{
    "model": "deepseek-ai/DeepSeek-V3",
    "messages": [{"role": "user", "content": "查询北京天气"}],
    "tools": [{
      "type": "function",
      "function": {
        "name": "get_weather",
        "description": "获取指定城市的天气信息",
        "parameters": {
          "type": "object",
          "properties": {"city": {"type": "string"}},
          "required": ["city"]
        }
      }
    }],
    "tool_choice": "auto"
  }'

Response (correctly returns tool_calls):

{
  "choices": [{
    "message": {
      "role": "assistant",
      "content": "",
      "tool_calls": [{
        "id": "019c2955cdbef92d6b516011cd3ae407",
        "type": "function",
        "function": {
          "name": "get_weather",
          "arguments": "{\"city\":\"北京\"}"
        }
      }]
    },
    "finish_reason": "tool_calls"
  }]
}

Root Cause Analysis

After investigating OpenClaw's source code in @mariozechner/pi-ai/dist/providers/openai-completions.js:

if (context.tools) {
    params.tools = convertTools(context.tools, compat);
    params.tool_choice = options.toolChoice;
}

The code DOES support sending tools, but context.tools is empty for custom providers.

OpenClaw appears to use a capabilities system (similar to supportsReasoning, supportsVision) to determine which features each model supports. Custom providers don't have capability metadata, so OpenClaw doesn't populate context.tools even when tools are available.

Impact

• Users cannot use cost-effective Chinese API providers (SiliconFlow, Volcengine, etc.) with tool calling
• Restricts users to only official/known providers despite API compatibility
• Contradicts the purpose of supporting openai-completions API type

Proposed Solutions

Option 1: Add capability override in model config

{
  "models": [{
    "id": "deepseek-ai/DeepSeek-V3",
    "capabilities": {
      "supportsTools": true,
      "supportsVision": false,
      "supportsReasoning": false
    }
  }]
}

Option 2: Default to enabling tools for openai-completions providers

Since openai-completions is an API standard, assume tool support by default unless explicitly disabled.

Option 3: Provider-level capability declaration

{
  "providers": {
    "siliconflow": {
      "api": "openai-completions",
      "capabilities": {
        "tools": true,
        "vision": false,
        "reasoning": false
      }
    }
  }
}

Workaround

Currently, the only workaround is to use officially supported providers (OpenAI, DeepSeek official API), which may not be cost-effective or accessible in all regions.

Additional Context

• This issue was discovered through extensive debugging including strace, API testing, and source code analysis
• Multiple models confirmed to support function calling: DeepSeek-V3, Qwen2.5-Coder-32B, QwQ-32B
• The issue is specific to OpenClaw's capability detection, not the underlying pi-ai library

References

• SiliconFlow API Documentation: https://docs.siliconflow.cn/
• OpenAI Function Calling Spec: https://platform.openai.com/docs/guides/function-calling