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Get started with Agent Skills

Agent Skills extend Gemini CLI with specialized expertise. In this tutorial, you'll learn how to create your first skill, bundle custom logic, and activate it during a session.

Create your first skill

A skill is defined by a directory containing a SKILL.md file and subdirectories containing reference materials or scripts used by the skill. Let's create an API Auditor skill that runs a script to help you verify if local or remote endpoints are responding correctly.

1. Create the directory structure

The first step is to create the necessary folders for your skill and its scripts.

macOS/Linux

mkdir -p .gemini/skills/api-auditor/scripts

Windows (PowerShell)

New-Item -ItemType Directory -Force -Path ".gemini\skills\api-auditor\scripts"

2. Create the definition (SKILL.md)

The SKILL.md file defines the skill's purpose and instructions for the agent. Create a file at .gemini/skills/api-auditor/SKILL.md. This tells the agent when to use the skill and how to behave.

---
name: api-auditor
description:
  Expertise in auditing and testing API endpoints. Use when the user asks to
  "check", "test", or "audit" a URL or API.
---

# API Auditor Instructions

You act as a QA engineer specialized in API reliability. When this skill is
active, you MUST:

1.  **Audit**: Use the bundled `scripts/audit.js` utility to check the status of
    the provided URL.
2.  **Report**: Analyze the output (status codes, latency) and explain any
    failures in plain English.
3.  **Secure**: Remind the user if they are testing a sensitive endpoint without
    an `https://` protocol.

3. Add the tool logic

Skills can bundle resources like scripts to perform deterministic tasks. Create a file at .gemini/skills/api-auditor/scripts/audit.js. This is the code the agent will run.

// .gemini/skills/api-auditor/scripts/audit.js
const url = process.argv[2];

if (!url) {
  console.error('Usage: node audit.js <url>');
  process.exit(1);
}

console.log(`Auditing ${url}...`);
fetch(url, { method: 'HEAD' })
  .then((r) => console.log(`Result: Success (Status ${r.status})`))
  .catch((e) => console.error(`Result: Failed (${e.message})`));

Verify discovery

Gemini CLI automatically discovers skills in the .gemini/skills directory (as well as the .agents/skills alias).

To check if Gemini CLI found your new skill, use the /skills list command within an interactive session:

/skills list

You should see api-auditor in the list of available skills. If you just added the files, you can run /skills reload to refresh the list without restarting the session.

If your skill doesn't appear

If /skills list doesn't show your skill, check the following:

  1. The folder must be trusted (workspace skills only). Skills under <workspace>/.gemini/skills/ are only loaded when the workspace folder is marked as trusted. Run /trust and restart the session if needed. Skills under ~/.gemini/skills/ (user scope) are not affected by trust.
  2. Check the path layout. SKILL.md is discovered either at the root of the skills directory (.gemini/skills/SKILL.md) or one directory deep (.gemini/skills/<skill-name>/SKILL.md). The recommended layout uses a subdirectory per skill so you can bundle scripts and other resources alongside it. Files nested more than one directory deep are not discovered.
  3. The filename must be exactly SKILL.md. Capitalization matters on case-sensitive filesystems (Linux, and macOS when configured as such): skill.md or Skill.md will be ignored.
  4. Frontmatter must include both name: and description:, and must be the first thing in the file. A SKILL.md is silently skipped if either field is missing, if the delimiters (--- on their own lines) are absent, or if any text (an H1 title, a comment, even a blank line) appears before the opening ---.
  5. The skill name comes from the name: field, not the directory name. If your frontmatter says name: foo, the skill appears as foo in /skills list regardless of what its parent directory is called. The characters : \ / < > * ? " | in the name are replaced with -.

How to use the skill

Now that the skill is discovered, you can trigger its activation by asking a relevant question.

  1. Trigger: Start a new session and ask: "Can you audit https://google.com"
  2. Activation: Gemini identifies that the request matches the api-auditor description and calls the activate_skill tool.
  3. Consent: You will see a confirmation prompt. Type y to approve.
  4. Execution: Once activated, Gemini uses the run_shell_command tool to execute your bundled script: node .gemini/skills/api-auditor/scripts/audit.js https://google.com

Pro tip: Use the skill-creator

If you don't want to create the files manually, you can use the built-in skill-creator skill. Simply ask Gemini:

"Create a new skill called 'api-auditor' that tests if URLs are responding."

The skill-creator will handle the directory structure and boilerplate for you.

Manage skills

You can also manage skills using the gemini skills command from your terminal:

  • Install: gemini skills install <url-or-path>
  • Link: gemini skills link <path> (useful for local development)
  • Uninstall: gemini skills uninstall <name>

Next steps