Tool calling

Pass tools with function definitions and the model may return tool_calls instead of content.

curl https://api.vichar.io/v1/chat/completions \
  -H "Authorization: Bearer $VICHAR_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "model": "vichar-sonnet-5.5",
    "messages": [{"role": "user", "content": "What is the weather in Paris?"}],
    "tools": [{
      "type": "function",
      "function": {
        "name": "get_weather",
        "parameters": {
          "type": "object",
          "properties": {"city": {"type": "string"}},
          "required": ["city"]
        }
      }
    }],
    "tool_choice": "auto"
  }'

tool_choice accepts "auto", "none", "required", or {"type":"function","function":{"name":"..."}}. Parallel tool calls are enabled on models that support them (parallel_tool_calls).

Not every model supports tools. The supported_parameters field in GET /v1/models shows tools for models that do; calling a model without tool support returns a 400 error.