What is but-why?
Collaboratively write, update, or consult a project's WHY.md and design/ conceptual models — the documents that capture purpose, values, priorities, target users, and how users think about the product. Use when the user wants to create project documentation about why their project exists, discuss project vision or values, write a WHY.md, update conceptual models, revisit project priorities, or when you need to understand a project's purpose and values before doing work. Triggers include "but why", "write a WHY", "document the purpose", "update the why", "project vision", "collaborate on why", "update the design", "conceptual model", "what are the project values", "what's the priority", or "use but-why". Source: h14h/doc-skills.