Introduction

Convert a JSON-Schema to a GBNF grammar, to use with llama.cpp.

This implementation aims to support more of the JSON-Schema specification than alternatives.

See src/convert.test.ts and src/regexp-convert.test.ts for examples of supported features.

Use it online: adrienbrault.github.io/json-schema-to-gbnf

Development

To install dependencies:

bun install

To run:

bun run src/index.ts "<json schema>"

To build and run the website:

bun run build-site
bunx serve build

To run tests in watch mode when developing:

bun test --watch

Resources

• GBNF Spec
• json.gbnf
• json_arr.gbnf

Alternatives

The following are alternative JSON-Schema to GBNF converters:

• https://github.com/ggerganov/llama.cpp/blob/master/examples/json-schema-to-grammar.py
• https://github.com/intrinsiclabsai/gbnfgen
• https://github.com/mudler/LocalAI/blob/v1.40.0/pkg/grammar/json_schema.go

llama.cpp alternatives for JSON constrained output

• https://github.com/outlines-dev/outlines
• ollama/ollama#830
• https://github.com/1rgs/jsonformer
• https://github.com/guidance-ai/guidance#context-free-grammars
• https://localai.io/features/openai-functions/
• https://github.com/noamgat/lm-format-enforcer
• https://github.com/thiggle/api#context-free-grammar-completion-api
• https://github.com/rizerphe/local-llm-function-calling