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Structured Outputs

This page only documents Structured Output flows that were verified with real requests against Crazyrouter production. Verification date:
  • 2026-03-22
Strictly verified models:
  • gpt-5.4
  • gemini-3-pro-preview
Not included as a strict-success example:
  • claude-sonnet-4-6
Reason:
  • Under the current OpenAI-compatible response_format=json_schema request shape, claude-sonnet-4-6 did not show stable strict-JSON behavior across production checks
  • Earlier testing produced JSON wrapped in Markdown code fences
  • The 2026-03-22 recheck returned empty content
  • Because the result is not stable or strictly parseable, it is not treated as a verified strict structured-output success example

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Verified matrix

ModelProtocolEndpointSuccess marker
gpt-5.4OpenAI Chat CompletionsPOST /v1/chat/completionsResponse can be parsed directly as JSON
gemini-3-pro-previewGemini NativePOST /v1beta/models/{model}:generateContentReturns JSON text matching schema

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GPT-5.4

curl https://crazyrouter.com/v1/chat/completions \
  -H "Content-Type: application/json" \
  -H "Authorization: Bearer YOUR_API_KEY" \
  -d '{
    "model": "gpt-5.4",
    "messages": [
      {
        "role": "user",
        "content": "Return a JSON object with keys city and country for Tokyo."
      }
    ],
    "response_format": {
      "type": "json_schema",
      "json_schema": {
        "name": "city_country",
        "strict": true,
        "schema": {
          "type": "object",
          "properties": {
            "city": { "type": "string" },
            "country": { "type": "string" }
          },
          "required": ["city", "country"],
          "additionalProperties": false
        }
      }
    }
  }'
Verified production output: 
{"city":"Tokyo","country":"Japan"}

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Gemini 3 Pro Preview

curl "https://crazyrouter.com/v1beta/models/gemini-3-pro-preview:generateContent?key=YOUR_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "contents": [
      {
        "role": "user",
        "parts": [
          {
            "text": "Return a JSON object with keys city and country for Tokyo."
          }
        ]
      }
    ],
    "generationConfig": {
      "responseMimeType": "application/json",
      "responseSchema": {
        "type": "object",
        "properties": {
          "city": { "type": "string" },
          "country": { "type": "string" }
        },
        "required": ["city", "country"]
      }
    }
  }'
Verified production output: 
{"city":"Tokyo","country":"Japan"}

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See Also