Create a Custom Skill

Skills are reusable instruction sets that agents can invoke during their work. mootup ships with a set of built-in skills; you can add your own to capture project-specific knowledge, review criteria, or recurring workflows.

What a skill is

A skill is a directory under .claude/skills/ containing a SKILL.md file. Agents load available skills at startup. They invoke a skill when the context matches — or you can ask an agent to invoke one explicitly as a Claude Code slash command.

Skills are version-controlled alongside your code. Everyone on the project shares the same skill definitions.

Create the skill

1. Create a directory for your skill under .claude/skills/:

   mkdir -p .claude/skills/code-review
   

2. Create a SKILL.md file in that directory:

   touch .claude/skills/code-review/SKILL.md
   

3. Open the file and write your instructions. A skill file should answer three questions:

   • What is this skill called? Give it a clear name at the top.

   • When should an agent use it? Describe the trigger — what situation or request should activate this skill.

   • What should the agent do? Give the concrete steps, criteria, or output format.

   Example — a code-review skill:

   # code-review
   
   Use this skill when asked to review a pull request or a diff.
   
   Review criteria:
   - Check for missing input validation on user-controlled fields
   - Flag any new dependencies and ask why they are needed
   - Confirm that new public functions have docstrings
   - Note any functions longer than 50 lines as candidates for extraction
   - Do not comment on style unless the diff violates the project linter
   
   Output format:
   Post findings as a numbered list. Start with blockers, then suggestions.
   End with a one-line summary: "LGTM", "Minor issues", or "Needs work".
   

4. Save the file. The skill is available to all agents after the next restart:

   moot down
   moot up
   

Invoking a skill

Agents pick up skills automatically when the context matches the trigger description. You can also ask an agent to use a skill directly:

@Implementation run the code-review skill on the latest diff

Or invoke it as a Claude Code slash command from your editor:

/code-review