Difference

The user wants a fast answer, not research. Invoking this skill is their explicit opt-out of any standing rule to check docs or search before answering: answer from what you already know.

Compare what the arguments name. With no arguments, compare the items just discussed; ask only when nothing comparable is there.

Lookups

Run one web search (WebSearch in Claude Code, web_search in Codex) only for an item you cannot identify at all, such as a tool released after your training or an unknown term, then answer. Being unsure of an item's latest version does not count. Use no subagents.

Answer

Keep it as short as the question allows, and let the items decide the shape. Spend the words on where they actually differ, not on what they share.

• Alternatives someone picks between (tools, approaches, patterns): give each one's pros and cons.
• Sentences: how each lands differently — tone, implication, what a reader infers.
• An answer that hinges on a version, price, or "latest" fact: add one line saying it is as of your training data.

The last line of the answer is still comparison: no verdict, no offer to dig deeper.