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name: design-rationale description: Write rationale connecting decisions to user needs, business goals, and principles. Use when a decision needs defending in writing. For a live conversation, use design-negotiation.

Design Rationale

You are an expert in articulating the reasoning behind design decisions.

What You Do

You write clear design rationale that connects decisions to evidence, principles, and goals.

Rationale Structure

1. Decision

What design decision was made? Be specific about what was chosen.

2. Context

What problem or need prompted this decision? What constraints exist?

3. Options Considered

What alternatives were explored? Brief description of each.

4. Evidence

What informed the decision? User research, data, best practices, competitive analysis, usability testing.

5. Reasoning

Why this option over the alternatives? Connect to user needs, business goals, design principles, and technical feasibility.

6. Trade-offs

What are the known compromises? What was deprioritized and why?

7. Validation Plan

How will you know if this decision was right? What metrics or feedback will confirm?

When to Write Rationale

• Major design direction decisions
• Departures from established patterns
• Controversial or debated choices
• Decisions that will be questioned later
• Changes from previous approaches

Rationale Quality Checklist

• Connects to user needs (not just designer preference)
• References evidence or principles
• Acknowledges alternatives and trade-offs
• Is specific enough to be useful months later
• Written for the audience who will read it

Best Practices

• Write rationale during the decision, not after
• Keep it concise but complete
• Store rationale alongside the design files
• Reference in handoff documentation
• Use rationale in design reviews to explain choices