Structured outputs

Force JSON output with response_format:

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": "Return the capital of France as JSON."}],
    "response_format": {
      "type": "json_schema",
      "json_schema": {
        "name": "answer",
        "schema": {
          "type": "object",
          "properties": {"capital": {"type": "string"}},
          "required": ["capital"],
          "additionalProperties": false
        }
      }
    }
  }'

Supported types:

{"type": "json_object"}: any valid JSON object
{"type": "json_schema"}: output constrained to the provided JSON Schema

Model support differs. Check supported_parameters for response_format and structured_outputs in GET /v1/models; requesting an unsupported mode returns 400 with a clear message.