Ollama JSON Mode - Structured Output Generation

ShopMax India needs to extract structured product data from unstructured text descriptions. Ollama JSON mode forces the model to return valid JSON every time, making it reliable for automated data pipelines without unpredictable text responses.

Ollama supports a format parameter set to "json" that instructs the model to produce valid JSON output. Combined with a clear prompt describing the expected schema, this eliminates parsing errors. The ollama.Client().chat() method accepts format="json" alongside the standard messages array.

The below example shows how ShopMax India extracts product details from raw text using Ollama JSON mode with the llama3.2 model.

It gives the following output,

{
  "name": "Samsung Smart TV",
  "size": "55 inch 4K",
  "price_rs": 45000,
  "features": ["HDR support", "3 HDMI ports"],
  "city": "Mumbai"
}

Always validate the JSON output even in JSON mode - some models may include extra text if the prompt is ambiguous. Define the expected schema clearly in your prompt. For production use at ShopMax India, combine JSON mode with Pydantic validation to catch schema mismatches before downstream processing.