Skills are reusable, filesystem-based resources that give your agent domain-specific expertise: workflows, context, and best practices that turn a general-purpose agent into a specialist. Unlike prompts (conversation-level instructions for one-off tasks), skills load on demand, only impacting the context window when needed.

You can attach two types of skill. Both work the same way: your agent invokes them automatically when they are relevant to the task.

• Pre-built Anthropic skills: Common document tasks such as PowerPoint, Excel, Word, and PDF handling.
• Custom skills: Skills you author and upload to your workspace.

To learn how to author custom skills, see Agent Skills and Skill authoring best practices. This page assumes you already have skills available in your workspace or are using Anthropic pre-built skills.

Attach skills to an agent

Attach skills when creating an agent. Each session supports up to 20 skills total, counted across every agent in the session (see Multiagent sessions).

Each entry in the skills array uses the following fields:

ant beta:agents create <<'YAML'
name: Financial Analyst
model: claude-opus-4-8
system: You are a financial analysis agent.
skills:
 - type: anthropic
 skill_id: xlsx
 - type: custom
 skill_id: skill_abc123
 version: latest
YAML