Module 02: The Anatomy of Skills & Semantic Discovery

Skills are the procedural nervous system of Antigravity. While system prompts establish identity, skills provide codified operational manuals, deterministic scripts, and domain expertise that trigger automatically when the task demands it.

1. What is an Antigravity Skill?

A skill is a self-contained directory that instructs Antigravity how to execute a specialized workflow. Unlike hardcoded tools, skills can package contextual rules, execution scripts (Python/Node/Bash), reference architecture files, and input-output schemas.

2. Anatomy of a Skill Directory

A standard Antigravity skill follows this modular structure:

my-custom-skill/
├── SKILL.md          # Mandatory: Instruction manifest with YAML frontmatter
├── scripts/          # Optional: Executable automation scripts and test harnesses
├── examples/         # Optional: Golden reference inputs, schemas, and outputs
└── references/       # Optional: In-depth technical documentation & manuals

3. The YAML Frontmatter Contract

The single most critical part of a skill is the frontmatter at the top of SKILL.md. Antigravity continuously indexes these descriptions to match user intent with available capabilities:

---
name: security-audit-scanner
description: Audits web application codebases for OWASP Top 10 vulnerabilities, exposed secrets, SQL injections, and insecure configurations. Use whenever the user asks for a security review, pre-deployment audit, or vulnerability scan.
---

# Security Audit Scanner Protocol

When this skill is activated:
1. Scan all environment configurations for hardcoded keys.
2. Verify parameterized SQL queries across all API endpoints.
3. Check HTTP headers for Content-Security-Policy and CORS headers.
4. Output findings in an executive severity table (Critical, High, Medium, Low).

4. Semantic Triggers vs. Manual Commands

Notice the description: "Use whenever the user asks for a security review, pre-deployment audit, or vulnerability scan." You do not need to memorize obscure slash commands. By describing the trigger condition clearly in plain English, Antigravity's semantic routing engine activates the skill autonomously when relevant.

5. The Marketplace & Plugin Ecosystem

When you need broad platform integrations (such as Google Workspace, Chrome DevTools, Firebase, or Hostinger), Antigravity supports bundled Plugins. A plugin bundles skills, custom subagents, behavioral rules, and MCP servers into a single verifiable package that installs with one click.