Skill Progressive Disclosure
Start with what a skill materially is, because the word carries more weight than the thing: a folder, with a markdown file in it. Nothing more. That file holds instructions and, at the top, a summary of those instructions. The mechanism lives in that asymmetry: it is a lazy system prompt, of which only the summary stays loaded, and which unfolds when the model decides the rest is useful to it. Pattern formalized by Anthropic in 'Equipping Agents with Agent Skills', in three levels. Level 1: the short description, one line, always in context. Level 2: the full SKILL.md, loaded if the agent deems the skill relevant. Level 3: resource files (templates, scripts), loaded on demand. The result is keeping full capability reachable without saturating context with detail nobody will read.
Strengths
- Massive context savings: 50 installed skills ≈ 5KB in context instead of 500KB
- Pedagogically structured: skill becomes readable like a book (overview → details)
- Official Anthropic pattern, natively supported by Claude Code and Skills SDK
Limitations
- Requires writing discipline: structuring a skill in levels demands info hierarchy thinking
- Level 1 (1 line) must be very well written, it's the only moment agent decides to invoke or not
Best for
- Design system manager shipping internal skills (ds-audit, component-create, token-update) to team
- Team exceeding 5 installed skills and noticing slowdown / context overflow