outlines

Enforce JSON, XML, or Pydantic model output formats during LLM generation.

228k|44.7k|Updated Jul 22, 2025
One-click install
npx skills add https://github.com/NousResearch/hermes-agent --skill outlines-nousresearch
Or copy as Structured Prompt for Agent
Please help me install this Agent Skill.
Skill: outlines
Source: https://github.com/NousResearch/hermes-agent/tree/main/skills/mlops/outlines
Command: npx skills add https://github.com/NousResearch/hermes-agent --skill outlines-nousresearch

SYSTEM DOCUMENTATION & REQUIREMENTS

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

What problem does it solve?

This Skill guarantees valid JSON, XML, or code structure during generation, preventing common LLM output errors and ensuring data integrity.

Core Features & Use Cases

  • Guaranteed Valid Outputs: Ensure generated text strictly adheres to specified formats like JSON or Pydantic models.
  • Local Model Support: Works seamlessly with Hugging Face Transformers, vLLM, and llama.cpp for local inference.
  • Use Case: Extracting structured user data from free-form text into a Pydantic model, ensuring all fields are correctly typed and formatted for downstream processing.

Quick Start

Use the outlines skill to generate a JSON object representing a user with name, age, and email.

Frequently Asked Questions about outlines

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

FAQPage Schema
How do I enforce JSON schema during LLM text generation?

To enforce JSON schema during LLM text generation, use constrained token sampling to guarantee the output strictly matches your specified Pydantic models or JSON structure, preventing formatting errors.

Can I use vLLM for local structured text generation?

Yes, you can use vLLM for local structured text generation. The approach supports local model backends including vLLM, Hugging Face Transformers, and llama.cpp, optimizing inference speed while ensuring output validity.

Why does my LLM output invalid JSON when extracting structured data?

LLM output contains invalid JSON during structured data extraction because standard sampling does not enforce format constraints. You need constrained generation to restrict token sampling and guarantee valid JSON or XML outputs.

What is the best way to guarantee valid Pydantic model outputs from local models?

The best way to guarantee valid Pydantic model outputs from local models is to enforce structured generation through constrained token sampling, ensuring all generated fields are correctly typed and formatted for downstream processing.

Does constrained text generation work with Hugging Face Transformers?

Yes, constrained text generation works with Hugging Face Transformers. It integrates seamlessly with local inference backends like Transformers, vLLM, and llama.cpp to enforce valid JSON, XML, or code structures.