interface-designerlisted

# Design an Interface ## Philosophy Every interface design involves tradeoffs you cannot see from a single perspective. Designing it twice (or three times) with radically different constraints forces you to explore the design space before committing. This skill spawns parallel sub-agents, each constrained differently, then compares and synthesizes. ## Workflow: 5 Phases ### Phase 1: Gather Requirements Before spawning any sub-agents, clarify: - What problem does this interface solve? - Who are the callers? What do they need? - What are the invariants the interface must preserve? - What are the performance / ergonomic / safety constraints? Do NOT start designing until requirements are agreed upon. ### Phase 2: Spawn Divergent Sub-Agents Launch 3+ parallel sub-agents (via `Agent` tool with `subagent_type`), each given the same requirements but a different constraint set. Constraints must force **radically different** designs -- not minor variations. See [constraints.md](constraints.md) for examples. Each sub-agent produces: - Interface definition (function signatures, types, module API) - Usage example for the most common case - One paragraph on the tradeoff it optimized for ### Phase 3: Present Designs Show all designs side-by-side. Label each by its primary constraint. Do not editorialize yet -- let the user see the raw options. ### Phase 4: Comparative Evaluation Evaluate every design against Ousterhout's criteria. See [evaluation-criteria.md](evaluation-criteri