Agent Skills: Progressive Disclosure as a System Design Pattern

Agent Skills is an open standard released by Anthropic in December 2025 that uses a simple SKILL.md file format to give AI agents modular, progressively loaded capabilities. The format applies the progressive disclosure design pattern to agent context management: at startup only skill names and descriptions are loaded (~80 tokens each), full instructions are activated when relevant, and supporting scripts/docs are pulled in only during execution. This three-tier architecture solves the context window degradation problem ('lost-in-the-middle') while making agent behavior configurable by non-technical users. OpenAI, Google, GitHub Copilot, and Cursor all adopted the standard within weeks of its release. The pattern generalizes beyond coding agents to any system needing broad capability with focused execution, and AI Engineers building non-coding agents must implement the same discovery-activation-execution pipeline themselves.