Cursor Rules vs Agent Skills: I Tested Both. Here's When Each One Actually Works.

Someone told me Cursor deprecated rules in favor of Agent Skills. I went and tested it. Rules are not deprecated. They do different things. Here's what I found. The setup I created identical instructions in both formats and ran them through Cursor's agent to see how each one behaves. As a rule ( .cursor/rules/jsdoc.mdc with alwaysApply: true ): --- description: "JSDoc rules" alwaysApply: true --- Always add JSDoc comments to exported functions. As a skill ( .cursor/skills/jsdoc/SKILL.md ): # JSDoc Skill Always add JSDoc comments to exported functions. Test 1: Does each one work on a relevant task? Prompt: "Create a utility function that formats dates" Rule: Added full JSDoc with @param and @returns . Followed the instruction. Skill: Same result. Full JSDoc, followed the instruction. When the task matches what the instruction is about, both rules and skills work fine. Test 2: Does each one load on an UNRELATED task? This is the test that matters. I gave each setup a marker instruction (