Specialized Tool vs Skill
Two basic forms of capability expression: specialized tool-code (structured call, determinism, testability, but hundreds of tokens and bloat) and Skill + universal executor (natural language document + terminal/interpreter; small number of tools covers many scenarios). Three dimensions of choice: parameter complexity (schema structure vs CLI), change frequency (Skill is cheaper to change), model capabilities (weak needs schema, strong is sufficient Skill).
Related: Agent Skills, [Balance of Tool Granularity], [Seven Basic Tools]