Authoring Skills and Rules (cross-platform)

Leading words: progressive disclosure, context pointer, token budget, Apply-when description, playbook todos, skip reason, leading words, phase separation, encode lessons in structure, deletion test, plain question.

A practitioner's guide to writing and maintaining the two artifact families that steer coding agents — Skills (on-demand, procedural capabilities) and Rules / instructions (standing context) — across Claude Code, Cursor, OpenCode, Codex, and GitHub Copilot.

Trigger: /authoring-skills-and-rules, or any request to write, port, or review a Skill or rule. If the target platform(s) are unstated, ask before scaffolding — the file layout differs per platform.

This skill carries the per-platform exact details in references/ (loaded on demand). The body below is the decision model + the universal craft + a phase-separated workflow.