Effective HTML: A Visual Field Guide for Thinking with Agents

Effective HTML is a visual field guide for choosing and creating the right artifact—from wireframes to prototypes, diagrams, and purpose-built interfaces—to enhance thinking with agents. It emphasizes matching the artifact to the decision, using HTML when spatial, visual, comparative, or interactive expression aids understanding. The guide explains when HTML is preferable to Markdown, highlighting its utility in revealing structure, testing behavior, and sharing tangible artifacts for collaboration.