outlines

Generate schema-constrained JSON and structured outputs from local language models.

14|5|Updated Apr 9, 2026
One-click install
npx skills add https://github.com/MLT-OSS/hermes-agent-go --skill outlines-mlt-oss
Or copy as Structured Prompt for Agent
Please help me install this Agent Skill.
Skill: outlines
Source: https://github.com/MLT-OSS/hermes-agent-go/tree/main/skills/mlops/inference/outlines
Command: npx skills add https://github.com/MLT-OSS/hermes-agent-go --skill outlines-mlt-oss

SYSTEM DOCUMENTATION & REQUIREMENTS

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

What problem does it solve? Language models often produce malformed JSON or free-form text that breaks downstream parsing. This Skill guarantees structurally valid outputs by constraining token generation against Pydantic models, JSON schemas, regex patterns, or fixed choice lists. ## Core Features & Use Cases - Grammar-Constrained Generation: Uses finite state machines to filter invalid tokens at each generation step, guaranteeing outputs match the target schema. - Pydantic Integration: Define output structures as Pydantic models with field constraints, enums, nested models, and optional fields. - Multiple Backends: Works with Transformers, llama.cpp, and vLLM for local inference, plus limited OpenAI API support. - Use Case: Extract structured company information (name, founded year, industry, employee count) from unstructured text paragraphs into validated Pydantic objects, with zero parsing failures. ## Quick Start Ask the agent to extract structured data from a text passage into a Pydantic model using Outlines with a local Transformers model.

Frequently Asked Questions about outlines

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

FAQPage Schema
How do I generate structured JSON output from a local LLM?

Use Outlines with a Pydantic model: load a model via outlines.models.transformers, create a generator with outlines.generate.json(model, YourModel), then call it with a prompt. The output is guaranteed to match your schema.

Outlines vs Instructor for structured generation?

Outlines excels with local models (Transformers, llama.cpp, vLLM) using zero-overhead FSM token filtering, while Instructor focuses on API models with automatic retrying. Choose Outlines for local inference speed and guaranteed validity.

Does Outlines support vLLM for production deployment?

Yes, Outlines supports vLLM via outlines.models.vllm with tensor parallelism for multi-GPU setups, AWQ/GPTQ quantization, and high-throughput batch processing. This makes it suitable for production serving workloads.

Can Outlines constrain generation with regex patterns?

Yes, use outlines.generate.regex with a pattern like a phone number format. The FSM guarantees every generated token sequence matches the regex, so outputs like '555-123-4567' always conform to the pattern.

What are the limitations of Outlines with OpenAI models?

OpenAI support in Outlines is limited compared to local backends. FSM-based token filtering is unavailable with API models, so some advanced constrained generation features may not work. Local backends provide full functionality.