What Are Skills in LLM Agents? How They Work and When to Use Them

Definition of Skills

Skills are structured local folders that encapsulate domain‑specific processes, knowledge, and tools, enabling large models to invoke them automatically or on demand, serving as capability packages for LLMs.

Difference Between Skills and Prompts

A Prompt is a temporary instruction telling the model what to do for a single task; it disappears after the task. A Skill records a method permanently, allowing the model to reuse it for similar situations without re‑explaining.

When to Create a Skill

One‑off or unstable tasks are not suitable. Suitable tasks usually have:

High frequency and repetition

Strict output consistency requirements

Mature existing procedures

Prompt alone cannot reliably achieve stable results

Skill Structure

Typical components:

Main description file : explains the purpose and activation conditions.

Rule or workflow document : e.g., brand guidelines, SOPs, internal processes.

Template or example : provides a ready‑made structure for the model.

Script or tool file : handles deterministic tasks.

Reference material : optional resources loaded only when needed.

How Skills Work

The core design is on‑demand loading, illustrated in the diagram below.

The workflow proceeds as follows:

The LLM knows the available Skills and the scenarios they fit.

When a user task matches a Skill, the model reads the main description file.

If the description mentions a template, reference, or script, those files are loaded or executed as needed.

This mechanism ensures that only relevant information enters the context, reducing token consumption.