When you need to design a module interface, this skill prevents you from settling on your first idea by spawning multiple parallel sub-agents that each produce radically different approaches. One agent might optimize for minimal methods, another for maximum flexibility, another for common-case efficiency. You get interface signatures, usage examples, and trade-off analysis for each design, then a direct comparison on simplicity, depth, and implementation efficiency. It's based on John Ousterhout's "design it twice" principle and works well when you're stuck between API approaches or want to explore the design space before committing to code.
npx skills add https://github.com/mattpocock/skills --skill design-an-interface