ujwal00/qwen3-1.7b-json

TEXT GENERATIONConcurrent Unit Cost:1Model Size:2BQuant:BF16Context Size:32kTool Calling:SupportedPublished:Jul 9, 2026License:apache-2.0Architecture:Transformer Open Weights Featherless Exclusive Cold

The ujwal00/qwen3-1.7b-json model is a 2 billion parameter Qwen3-1.7B fine-tune, specifically optimized for native JSON-Schema compliant output. It significantly improves performance on complex, nested JSON schemas without requiring grammar-constrained decoding. This model excels at generating structured JSON data that strictly adheres to a given JSON Schema, making it ideal for applications requiring reliable and validated JSON outputs.

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Qwen3-1.7B-JSON: Native JSON-Schema Compliance

This model is a fine-tuned version of Qwen/Qwen3-1.7B (2 billion parameters, 32768 tokens context length) designed to generate JSON output that strictly conforms to a provided JSON Schema. Its key differentiator is its ability to achieve high schema compliance natively, without relying on external grammar-constrained decoding engines, particularly for complex and nested schemas.

Key Capabilities & Performance

  • Enhanced JSON-Schema Compliance: Achieves significant gains in native schema compliance, especially on challenging nested ($ref, $defs) schemas, improving from 58% to 72–74% on held-out data.
  • Robust on Complex Schemas: Demonstrates substantial improvements across various datasets from JSONSchemaBench, with gains of +13% to +40% on 'medium' to 'hard' categories, including Github_hard and Snowplow.
  • Low Parse-Fail Rate: Maintains a low parse-fail rate of 2.5–4%, indicating reliable JSON generation.
  • QLoRA Fine-tuning: Trained using QLoRA SFT on approximately 4k schema-instance pairs, ensuring robust performance on validated targets.

Ideal Use Cases

  • Structured Data Generation: Perfect for applications requiring precise, validated JSON outputs from a language model.
  • Function Calling & API Interaction: Can be used to generate API requests or responses that adhere to predefined JSON schemas.
  • Small Model Deployment: Lifts native compliance for small models in high-volume, structured tasks, making them more usable without additional decoding engines.