Develop Design Rationale Agent Skill

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Design Rationale

A design rationale document captures the "why" behind design decisions.the context, constraints, alternatives considered, and reasoning that led to a particular solution. While designs themselves show what was built, rationale documents preserve institutional knowledge about why it was built that way.

When to Use

• When making significant UX decisions that affect user experience
• Before design reviews to prepare stakeholder discussions
• When multiple valid approaches exist and the choice needs justification
• To onboard new team members to existing design decisions
• When revisiting past decisions to understand original reasoning
• During design system evolution to document pattern choices

When NOT to Use

• The decision is architectural or a technology selection -> use develop-adr (Nygard format)
• You need stakeholder alignment on the overall solution direction -> use develop-solution-brief
• You are documenting exploration findings rather than a decision -> use develop-spike-summary
• The decision is trivially reversible and low-stakes: a rationale document adds ceremony; record the reasoning in the PR or ticket instead

Instructions

When asked to document design rationale, follow these steps:

• State the Decision

Begin with a clear, one-sentence summary of what design decision was made. This becomes the title and reference point for the document.

• Describe the Context

Explain the situation that prompted this decision. What problem were you solving? What constraints existed? What user needs informed the direction? Include relevant research findings.

• List Options Considered

Document at least 2-3 alternatives that were evaluated. For each option, describe what it would look like and its key characteristics. Be fair to all options.avoid strawmen.

• Define Evaluation Criteria

Specify how options were assessed: usability heuristics, technical feasibility, brand alignment, user research findings, business requirements, or design principles.

• Explain the Reasoning

Walk through why the chosen option best meets the criteria. Be explicit about trade-offs.what you gained and what you sacrificed. Acknowledge where the decision is reversible vs. irreversible.

• Document Trade-offs Accepted

Every design decision involves trade-offs. Name what you gave up and why it was acceptable. This honesty helps future teams understand constraints.

• Note Follow-up Considerations

Capture anything that needs attention later: metrics to watch, conditions that might warrant revisiting the decision, or related decisions to make.

Output Format

Use the template in references/TEMPLATE.md to structure the output. A complete rationale fills every template section: Decision Summary; Context; Options Considered; Evaluation; Decision Rationale; Trade-offs Accepted; Reversibility; Follow-up Considerations; Supporting Materials; and Decision History.

Quality Checklist

Before finalizing, verify:

• [ ] Decision is clearly stated in one sentence
• [ ] Context explains the "why now" and constraints
• [ ] Multiple alternatives are documented fairly
• [ ] Evaluation criteria are explicit
• [ ] Reasoning addresses why chosen option beats alternatives
• [ ] Trade-offs are honestly acknowledged
• [ ] A reader who inherits this design can reconstruct why the chosen option won without asking anyone

Examples

See references/EXAMPLE.md for a completed example.