outlines

Constrain token generation with grammars and finite state machines for valid JSON, XML, and code outputs.

Updated Apr 11, 2026
One-click install
npx skills add https://github.com/musical-basics/hermes-build-2 --skill outlines-musical-basics
Or copy as Structured Prompt for Agent
Please help me install this Agent Skill.
Skill: outlines
Source: https://github.com/musical-basics/hermes-build-2/tree/main/skills/mlops/inference/outlines
Command: npx skills add https://github.com/musical-basics/hermes-build-2 --skill outlines-musical-basics

SYSTEM DOCUMENTATION & REQUIREMENTS

💡 This Skill includes references (resource) components.

What problem does it solve?

Outlines prevents invalid or ill-typed generated outputs by constraining token sampling with grammars and finite state machines, ensuring generated JSON, XML, and code always conform to schemas and Pydantic models so downstream systems never fail on parsing or validation errors.

Core Features & Use Cases

  • Zero-overhead structured generation: Filters invalid tokens at generation time to guarantee syntactic validity without expensive post-validation loops.
  • Pydantic & JSON Schema integration: Translate Pydantic models or JSON schemas into grammars for type-safe model outputs.
  • Local and production backends: Optimized support for transformers, llama.cpp, and vLLM for both development and high-throughput deployments, applicable to extraction, classification, code generation, and form processing.

Quick Start

Generate a validated JSON object from the text "John Doe, 30, [email protected]" using outlines with a local transformers or vLLM model.

Frequently Asked Questions about outlines

High-intent search queries and answers about installing and using this skill.

FAQPage Schema
How do I guarantee valid JSON structured outputs from local LLMs?

Guarantee valid JSON structured outputs by constraining token generation with grammars and finite state machines, filtering invalid tokens at generation time to prevent parsing errors without expensive post-validation loops.

Can I use Pydantic models for type-safe structured generation with vLLM?

Yes, you can use Pydantic models for type-safe structured generation by translating them into generation grammars, which are fully compatible with high-throughput vLLM backends for production deployments.

What is the best way to enforce JSON schema compliance during LLM inference?

The best way to enforce JSON schema compliance during inference is applying zero-overhead token filtering, which restricts the model's token sampling to only valid syntax defined by your schema at generation time.

Does structured generation work with both transformers and llama.cpp backends?

Structured generation works seamlessly with both local transformers and llama.cpp backends, allowing you to enforce type-safe Pydantic schema outputs for data extraction and classification tasks across different environments.

Why do LLMs generate malformed JSON and how can I prevent it?

LLMs generate malformed JSON due to unconstrained token sampling; prevent it by applying finite state machines to filter invalid tokens dynamically, ensuring downstream systems never fail on parsing or validation errors.

Are there limitations to using grammars for structured code generation?

Structured code generation using grammars limits the model's creative token sampling space, which may affect outputs for highly ambiguous tasks but guarantees strict syntactic validity for downstream parsing.