How to Build Custom Gemini Skills: A Step-by-Step Tutorial

Building custom Gemini CLI skills is one of the most impactful ways to multiply your productivity. Unlike traditional plugin development that requires learning framework-specific APIs, Gemini skills are defined declaratively using the SKILL.md format. This tutorial walks you through creating your first skill from concept to publication.

A skill begins with identifying a repetitive workflow pattern in your development process. Perhaps you frequently need to generate API documentation from TypeScript interfaces, or you regularly set up monitoring dashboards for new microservices. The SKILL.md format lets you encode these patterns as structured instructions that Gemini can follow consistently. Start by creating a new SKILL.md file with the required frontmatter: name, description, version, and the trigger conditions that activate your skill.

The body of your skill definition uses natural language instructions augmented with template variables and conditional logic. You define input parameters, specify the steps Gemini should follow, and describe the expected output format. Testing is straightforward using the gemini skill test command, which runs your skill against sample inputs and validates outputs against your specified criteria. The built-in linter catches common issues like ambiguous instructions or missing edge case handling before you publish.

Publishing your skill to the marketplace makes it available to the entire Gemini CLI community. Before publishing, ensure your skill includes comprehensive examples, clear documentation of its limitations, and appropriate version constraints for any dependencies. The review process typically takes 24 to 48 hours, after which your skill appears in marketplace search results. Community feedback through ratings and usage metrics helps you iterate and improve your skill over time.