Markdown

Description

Markdown is a lightweight markup language with plain-text formatting syntax. It is the dominant file format used by AI agents to communicate with users due to its simplicity and portability.

From Using-Claude-Code-The-Unreasonable-Effectiveness-of-HTML

• While Markdown is simple and portable, it can become a restricting format for complex agent outputs.
• It is difficult to read Markdown files longer than 100 lines.
• HTML is increasingly preferred over Markdown for rich visualizations and interactive specs.