outlines

Constrain LLM token generation with JSON, Pydantic, or regex grammars.

1|Updated May 16, 2026
One-click install
npx skills add https://github.com/devMoez/titan --skill outlines-devmoez
Or copy as Structured Prompt for Agent
Please help me install this Agent Skill.
Skill: outlines
Source: https://github.com/devMoez/titan/tree/main/optional-skills/mlops/inference/outlines
Command: npx skills add https://github.com/devMoez/titan --skill outlines-devmoez

SYSTEM DOCUMENTATION & REQUIREMENTS

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

What problem does it solve?

This Skill solves the reliability problem of getting LLM outputs that strictly match a required structure, so you can use model results directly without brittle post-processing.

Core Features & Use Cases

  • Structured generation (JSON/XML/regex/code): Constrain generation so outputs follow a target format rather than “best effort” text.
  • Type-safe results with Pydantic: Define schemas as Pydantic models and receive validated, correctly typed objects.
  • Multi-backend local inference: Run with Transformers, llama.cpp, or vLLM to control latency and throughput while keeping structure guarantees.
  • Use Case: Extract product details from messy descriptions into a typed schema (e.g., name, price, availability) while guaranteeing valid JSON and correct types.

Quick Start

Use the outlines skill to extract a Product object from the prompt: “Extract iPhone 15 Pro details (name, price, in_stock) from: iPhone 15 Pro costs $999 and is currently in stock.”

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 generation from an LLM using Pydantic schemas?

Guarantee valid JSON generation by constraining LLM token sampling with grammar-based decoding. You define a Pydantic schema, and the constrained sampling mechanism ensures the output strictly matches that structure, yielding type-safe validated objects.

Can I use constrained structured generation with vLLM and Transformers backends?

Yes, structured generation works with vLLM, Transformers, and llama.cpp backends. The grammar constraints integrate with these local inference engines to control latency and throughput while enforcing strict JSON, regex, or code output formats.

What is the best way to extract structured data from messy text without post-processing?

The best way to extract structured data without brittle post-processing is grammar-based decoding. By applying JSON or Pydantic schema constraints during generation, the LLM is forced to produce structurally valid, correctly typed outputs directly from messy text.

Does regex constrained decoding work for classification tasks in local inference?

Yes, regex constrained decoding works for classification tasks by restricting token generation to valid regex patterns. This ensures the LLM output strictly matches allowed classification labels during local inference without requiring additional validation steps.

Why do I need grammar-based decoding instead of prompt engineering for structured extraction?

Grammar-based decoding is needed because prompt engineering only encourages structured outputs through best-effort text generation. Constrained sampling guarantees structural validity at the token level, ensuring outputs match your JSON schema or Pydantic model exactly.

What are the limitations of using Pydantic model-to-schema integration for LLM outputs?

The limitation of Pydantic model-to-schema integration is that it requires the outlines library and compatible local backends. Complex nested schemas may constrain generation heavily, potentially increasing latency while ensuring type-correct structured outputs.