Build once, run on any agent: A practical guide to agent skills

GitHub's guide explains agent skills as versioned directories centered on a SKILL.md file that capture repeatable task instructions shareable across agents, while the environment still supplies tools, credentials, and permissions. Using examples like Proof Agent for adversarial verification and Data Forge for a multi-skill data pipeline, it recommends keeping project configuration in a manifest, sharing execution paths between skills, and placing human checkpoints and CI checks in workflows. It also covers packaging skills for clients such as Claude Code, Cursor, and GitHub Copilot, and notes that applications suit workflows needing stable interfaces, shared state, audit trails, or permissions enforced outside the model.