design-an-interface

design-an-interface is a Chinese-language (translated) planning skill, based on the "Design It Twice" principle from A Philosophy of Software Design, that generates multiple substantially different interface designs for a module and then compares them. The problem it solves is premature commitment: your first API idea is rarely the best, so the skill forces the exploration of several fundamentally different shapes before settling. It is a deprecated entry in the mattpocock-skills-zh-cn collection.

The workflow gathers requirements (what problem the module solves, who the callers are, key operations, constraints, what to hide versus expose), then uses the Task tool to spawn three or more parallel sub-agents, each assigned a deliberately different constraint—minimize method count, maximize flexibility, optimize for the common case, or draw on a specific paradigm/library. Each sub-agent returns an interface signature, a usage example, what it hides internally, and its trade-offs. The designs are presented sequentially, then compared along dimensions such as interface simplicity, general-purpose versus specialized, implementation efficiency, and module depth (a small interface hiding large complexity is good; a large interface over a thin implementation is shallow and to be avoided). Finally it synthesizes, often combining insights from multiple options.

It targets developers and API designers who want a rigorous, contrast-driven way to shape module interfaces. It is purely a discussion-and-comparison aid—its own anti-patterns note that it does not implement, only explores interface shape, and warns against letting sub-agents produce similar designs or skipping the comparison that carries the value.