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A skill is a directory containing a SKILL.md file with optional scripts/ and references/ subdirectories.

Directory Structure

The SKILL.md File

The SKILL.md file is the heart of a skill. It contains YAML frontmatter with metadata, followed by markdown instructions.

Required Fields

  • name: Must be lowercase, alphanumeric with hyphens only (max 64 characters)
  • description: Brief summary shown in the agent’s system prompt (max 1024 characters)

Optional Fields

Full Example

Adding Scripts

Scripts are executable files the agent can run. They must have a shebang line.

Python Script Example

Create scripts/check_style.py:

Shell Script Example

Create scripts/lint.sh:
Scripts are executed with the skill directory as the working directory. The agent can pass arguments when executing scripts.

Adding References

References are documentation files the agent can load on demand.

Example Reference

Create references/style-guide.md:

Validation Rules

Skills are validated when loaded. Here are the rules:

Name Requirements

  • Maximum 64 characters
  • Lowercase letters, numbers, and hyphens only
  • Cannot start or end with a hyphen
  • No consecutive hyphens (--)
  • Must match the directory name

Field Limits

Valid Licenses

Common SPDX identifiers are accepted: MIT, Apache-2.0, GPL-3.0, BSD-3-Clause, etc.

Organizing Multiple Skills

Create a directory containing multiple skill folders:
Load all skills at once: