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Skills are markdown-based instruction sets that extend agent capabilities without writing new tool code. Each skill is a directory containing a SKILL.md file with frontmatter metadata and detailed instructions. Unlike tools, skills are not callable directly. The agent uses the auto-registered Skill viewer tool to read a skill’s instructions, then follows those instructions using its existing tools.

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Register Skill

Pass skill sources to the Toolkit constructor through skills_or_loaders. Each entry can be a directory path string, a Skill object, or a SkillLoaderBase subclass:

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How Skill Works

When a Toolkit is constructed with skills, the registration and lookup flow runs in two phases. At initialization:
  • The toolkit scans every registered skill source and collects each skill’s name, description, and directory.
  • It auto-registers the built-in Skill viewer tool.
  • It composes a system-prompt fragment listing the available skills (name and description only) and instructing the agent to invoke the Skill viewer to read the full content.
At runtime:
  • The agent picks a skill by name and calls the Skill viewer.
  • The viewer reads the corresponding SKILL.md and returns its full markdown.
  • The agent follows those instructions using its already-equipped tools.
Skills are not tools: the agent cannot call a skill directly. It must first use the Skill viewer to read the instructions, then execute the steps described within using its other tools.