A Practical Guide to Building Agents
by OpenAI
OpenAI's field guide to when — and how — to build production LLM agents.
Overview
A Practical Guide to Building Agents is a free PDF from OpenAI that gives product and engineering teams a vendor-informed framework for building agentic systems. It defines an agent as a system that independently accomplishes tasks on a user's behalf, and breaks one into three core components — the Model (the LLM doing reasoning and decision-making), Tools (external functions or APIs the agent calls to take action), and Instructions (the explicit guidelines and guardrails governing behavior). The guide covers when you should (and shouldn't) build an agent versus a simpler deterministic workflow, how to choose and prompt a model, orchestration patterns for single-agent versus multi-agent systems (manager and decentralized/handoff patterns), and layered guardrails plus human-in-the-loop controls for safe deployment. It reflects lessons OpenAI learned from numerous real-world customer deployments, making it a concise, practitioner-oriented reference rather than marketing material.
At a Glance
- Topic
- Agentic
- Level
- Intermediate
- Format
- Guide
- Cost
- Free
- Duration
- ~34-page PDF, ~1 hour read
- Provider
- OpenAI
- Hands-on
- No
- Certificate
- None
What You’ll Learn
- ✓Decide when a task genuinely warrants an agent versus a deterministic workflow
- ✓Structure an agent around its three components: model, tools, and instructions
- ✓Choose between single-agent loops and multi-agent (manager vs decentralized/handoff) patterns
- ✓Design layered guardrails and human-in-the-loop checkpoints for safe deployment
- ✓Write effective instructions and select tools for reliable agent behavior
Highlights
- •Published by OpenAI (April 2025), grounded in real customer deployments
- •Framework-agnostic mental models, not just an SDK walkthrough
- •Concise, quotable reference on agent design foundations and guardrails
Who It’s For
Best For
- ✓Product and engineering teams building their first agent
- ✓AI engineers deciding single-agent vs multi-agent architecture
- ✓Anyone needing a shared vocabulary for agent design and safety
Prerequisites
- •Familiarity with LLM APIs and prompting
- •Basic understanding of tool/function calling
FAQ
What is A Practical Guide to Building Agents?
OpenAI's free, ~34-page guide to designing and shipping LLM agents, aimed at product and engineering teams building their first agentic system. Distills patterns from real customer deployments: when a workflow actually needs an agent, the model/tools/instructions anatomy, single- vs multi-agent designs, and guardrails.
Is A Practical Guide to Building Agents free?
A Practical Guide to Building Agents is free to access.
What level is A Practical Guide to Building Agents for?
A Practical Guide to Building Agents is aimed at a intermediate audience. Recommended background: Familiarity with LLM APIs and prompting, Basic understanding of tool/function calling.
How long does A Practical Guide to Building Agents take?
Expect roughly ~34-page PDF, ~1 hour read. Most learners work through it at their own pace.
What will I learn from A Practical Guide to Building Agents?
You'll learn: Decide when a task genuinely warrants an agent versus a deterministic workflow; Structure an agent around its three components: model, tools, and instructions; Choose between single-agent loops and multi-agent (manager vs decentralized/handoff) patterns; Design layered guardrails and human-in-the-loop checkpoints for safe deployment; Write effective instructions and select tools for reliable agent behavior.