1rgs/jsonformer

Health v2 · maintenance only

Flags: no_releases

Adoption not part of the score

4934 stars · 183 forks observed · 2026-08-28

What it is AI-extracted, prompt v1, taxonomy v1, 2026-08-29, confidence not recorded

Jsonformer is a Python library that wraps Hugging Face causal language models to generate syntactically correct JSON conforming to a given JSON Schema. It fills in fixed structural tokens itself and only delegates content token generation to the model, making structured output reliable.

Use cases

• generate structured from a language model
• force an llm to output valid matching a schema
• extract structured data from text with a local huggingface model
• get reliable output without prompt engineering or post-processing
• generate nested objects and arrays from small language models

When to choose

• you use Hugging Face transformer models and need guaranteed schema-valid JSON
• you want structured output from small local models without brittle prompt parsing
• your schemas use numbers, booleans, strings, arrays, and objects

When to avoid

• you need full JSON Schema support beyond the supported subset
• you use OpenAI or other API-based models with native structured output
• you need actively developed features or broad model backend support

Facets

library · maturity maintenance

llm-inference serialization prompt-engineering large-language-models developer-tools python -schema structured-output huggingface constrained-generation llm natural-language-processing

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markdown · JSON · MCP: product_card(name="1rgs/jsonformer")