OpenAI API Skills: Reusable Capabilities

🎯 Architect Challenge

Imagine you're designing a complex AI agent. To keep it modular, you want to package specialized logic into a "Skill Bundle".

Task

Select the 4 essential components that constitute a standard OpenAI Agent Skill bundle folder.

📝Instructions
⚙️Scripts
📦Assets
📋Manifest File
🗄️Database
🔌API Keys
Modular Agent Skills

Introduction

Why this matters

Building monolithic prompts is a maintenance nightmare. Agent Skills allow you to codify repeatable processes into versioned, shared bundles that agents can "learn" dynamically.

What's in this lesson

  • Structure of a Skill directory.
  • Crafting the SKILL.md manifest.
  • Discovery vs. Invocation phases.
  • Design principles for scalable AI.
Structure Overview

The Skill Bundle

An Agent Skill is a directory anchored by a mandatory SKILL.md file. It packages everything an agent needs for a specific domain.

  • Instructions: Found in SKILL.md, these are the "playbook" for the LLM.
  • Scripts: Executable code (Python, Bash) the agent can trigger.
  • Assets: Templates, datasets, or reference documents.
Directory Hierarchy

Quick Check: Required Files

Which file is absolutely required for a directory to be recognized as an OpenAI Agent Skill?

The SKILL.md Manifest

This file is the brain of the skill. It requires YAML frontmatter for metadata and Markdown for instructions.

---
name: log-analyzer
description: Analyzes server logs for error patterns.
---
# Instructions
1. Check the logs for 404 errors...
2. Categorize by urgency...

Metadata Discovery

The name and description in the frontmatter are indexed. This helps the agent decide when to use a specific skill.

Manifest Illustration

Quick Check: Metadata

Which metadata fields are mandatory in the SKILL.md frontmatter for the agent to discover the skill?

Discovery vs. Invocation

To optimize performance, agents process skills in two phases:

  1. Discovery: At startup, the agent reads only the metadata (frontmatter) of all skills.
  2. Invocation: Only when the agent decides a skill is relevant does it load the full instruction body.
Lifecycle Flow

Quick Check: Loading

When does the agent load the full instruction body of a skill from SKILL.md?

Design Best Practices

Effective skills follow the Single Responsibility Principle. Avoid "all-in-one" skills that try to solve too many problems.

  • Focus: Build specialized skills (e.g., "SQL Formatter" vs "General Coder").
  • Clarity: Use clear descriptions to aid discovery.
  • Portability: Keep all dependencies within the folder.
Design Principles

Validation Protocol

Verify your understanding of Agent Skill architecture. This assessment requires 80% to certify.

Protocol
  • 8 questions on anatomy and lifecycle.
  • 7/8 correct (80%) required to pass.

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