outlines

Constrain LLM token sampling to JSON schemas, regex patterns, or Pydantic models.

2|1|Updated Jul 14, 2026
One-click install
npx skills add https://github.com/heysuhas/hermes_cli --skill outlines-heysuhas
Or copy as Structured Prompt for Agent
Please help me install this Agent Skill.
Skill: outlines
Source: https://github.com/heysuhas/hermes_cli/tree/main/optional-skills/mlops/inference/outlines
Command: npx skills add https://github.com/heysuhas/hermes_cli --skill outlines-heysuhas

SYSTEM DOCUMENTATION & REQUIREMENTS

💡 This Skill requires outlines, transformers, vllm, pydantic, and includes references (resource) components.

What problem does it solve?

This Skill solves the common issue of LLMs generating malformed or unpredictable text when you require strict, machine-readable formats like JSON or specific regex patterns.

Core Features & Use Cases

  • Structured Generation: Forces the model to adhere to Pydantic models or JSON schemas, ensuring 100% valid output.
  • Grammar-Based Control: Uses Finite State Machines to constrain token sampling at the logit level, preventing invalid tokens before they are generated.
  • Use Case: Use this to build reliable data extraction pipelines where you need to guarantee that an LLM returns a specific Pydantic object, such as a User profile or a Product specification, without needing complex retry logic.

Quick Start

Use the outlines skill to generate a structured JSON response matching the User Pydantic model for the provided text input.

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 output from an LLM?

To guarantee valid JSON output from an LLM, you constrain token sampling at the logit level using Finite State Machines. This enforces structured text generation based on specific JSON schemas, ensuring 100% valid output without post-generation validation loops.

How do I force an LLM to generate responses matching a Pydantic model?

You force an LLM to match a Pydantic model by applying grammar-based control during inference. This constrains the model's token sampling to adhere strictly to the defined Pydantic models, preventing invalid tokens before they are generated.

Does structured generation work with vLLM and Transformers for high-throughput inference?

Yes, structured generation works with vLLM and Transformers for high-throughput inference. It supports these production-grade backends alongside llama.cpp to enforce JSON schemas and regex patterns during large-scale data extraction tasks.

What is the best way to prevent malformed text in LLM data extraction pipelines?

The best way to prevent malformed text in LLM data extraction pipelines is zero-overhead grammar-based generation. By constraining token sampling to specific formats, it eliminates unpredictable text and removes the need for complex retry logic.

Why does my LLM generate invalid JSON schema structures?

An LLM generates invalid JSON schema structures because standard token sampling allows unpredictable text. Implementing grammar-based control with Finite State Machines prevents invalid tokens before generation, ensuring 100% valid structured output.