Comprehensive guide for building autonomous agents in Claude Code plugins with structured frontmatter, system prompts, and triggering conditions.

• Agents are autonomous subprocesses defined in markdown files with YAML frontmatter; use them for multi-step independent tasks, commands for user-initiated actions
• Required frontmatter fields: name (3–50 lowercase-hyphenated characters), description (with 2–4 concrete triggering examples), model (inherit/sonnet/opus/haiku), color (blue/cyan/green/yellow/magenta/red), optional tools array for least-privilege access
• System prompt design uses second-person voice with clear responsibilities, step-by-step process, quality standards, output format, and edge case handling; keep under 10,000 characters
• Description field is critical: must specify triggering conditions, include <example> blocks with context, user request, assistant response, and <commentary> explaining why the agent triggers
• Validation rules enforce identifier format, description length (10–5,000 chars), and system prompt structure; includes AI-assisted generation templates and testing utilities for triggering verification