Skill Tool

What is it?

The Skill Tool lets you manage specialized expertise domains — called skills — that Yukkai can switch on and off. Think of a skill as a focused knowledge profile: when activated, it tunes Yukkai's behavior for a specific area like iOS development, database design, or technical writing.

Skills are distinct from personalities (which control tone and style). Skills control what Yukkai knows and which tools it prefers for a given task. You can have multiple skills active at once, and Yukkai can even auto-detect the right skill based on keywords in your messages.

How it works

Each skill contains:

• A name and description for identification.
• A system prompt — the core instructions that define the skill's expertise.
• Activation keywords — words in your messages that trigger auto-activation (e.g., swift, swiftui, xcode).
• File patterns — glob patterns that help auto-detect when a skill is relevant (e.g., *.swift, Package.swift).
• Preferred tools — a comma-separated list of tools the skill should favor (e.g., bash, file_read, grep).
• Tags — labels for categorization (e.g., ios, mobile, frontend).

Skills can be built-in (pre-installed by Yukkai) or custom (created by you). Custom skills can be edited and deleted; built-in skills can only be activated or deactivated.

How to use it

List all skills

See every available skill and whether it's currently active:

list all skills

This returns a table showing each skill's name, ID, and status (active/inactive).

Activate a skill

Turn on a skill by its ID:

activate skill swift-ios

Once active, Yukkai will apply that skill's expertise to your conversations.

Deactivate a skill

Turn off a skill you no longer need:

deactivate skill swift-ios

View skill details

Get the full configuration of a specific skill:

show details for skill swift-ios

This displays the system prompt, keywords, file patterns, tags, and preferred tools.

Examples

Create a custom skill

Build a skill for a domain Yukkai doesn't cover out of the box:

create a skill called "Technical Writer"
- description: "Expert in clear, concise technical documentation"
- system prompt: "You are a technical writing expert. Prioritize clarity, brevity, and active voice. Use simple language. Structure documents with headings and bullet points."
- tags: writing, documentation
- activation keywords: doc, documentation, readme

Create a skill by learning from a project

Yukkai can analyze a real project directory and auto-generate a skill based on what it finds:

learn a skill from /Users/me/projects/MyApp

Yukkai inspects the project's files, frameworks, and patterns, then proposes a skill with appropriate keywords, file patterns, and a tailored system prompt.

Update an existing skill

Modify any custom skill's configuration:

update skill technical-writer
- add activation keyword: "wiki"
- add preferred tool: file_write

Delete a custom skill

Remove a skill you no longer want:

delete skill technical-writer

Note: Built-in skills cannot be deleted — only deactivated.

Search across knowledge bases

Skills can also store searchable knowledge. Use the search action to find information across indexed skill knowledge:

search skills for "CoreData migration"

Tips & best practices

• Start with list — before creating anything new, check what's already available. Yukkai ships with several built-in skills that may already cover your needs.
• Use auto-activation wisely — set meaningful activation keywords so the right skill turns on automatically when you mention relevant topics, without you having to activate it manually each time.
• Keep system prompts focused — a skill should cover one domain well. If you need expertise across multiple areas, create separate skills and activate them together.
• Learn from real projects — the learn action is a powerful way to capture domain knowledge from an existing codebase. Point it at a well-structured project and review the generated skill before activating it.
• Don't over-activate — having too many skills active at once can dilute their effect. Activate only what's relevant to your current task.
• Review before trusting — when you create or learn a skill, use info to review its system prompt and keywords. Adjust anything that doesn't fit your workflow with update.
• Tags help with discovery — use consistent, lowercase tags across skills (e.g., ios, frontend, database) so you can browse and find them easily later.