writing-rules

# Writing rules — and anything else an agent reads You are writing for a reader who has already read everything. Explanation is waste; precision is the whole job. Left alone, a model writing instructions for a model spends most of its words restating what it already knows — every one of those lines is a **no-op**: paid every turn, changing nothing. The packaging differs (a `core/` rule, a profile gate, a `SKILL.md`, a subagent prompt, a handoff note) but the writing does not. The same levers make each one predictable, so the agent takes the same *process* every run rather than producing the same output. When the document is a harness surface — a `core/` rule, a profile, a skill, a hook — read [`HARNESS-SURFACES.md`](HARNESS-SURFACES.md) for where it goes and what it costs. ## Instruction vocabulary `AGENTS.md` is the canonical portable instruction file. Never infer the active agent from this skill's install path: portable canonical content may be copied into a required client adapter such as `.claude/skills`. Treat client-specific instruction files as generated adapters; edit their shared `core/` or `profiles/` source, never an adapter copy. ## The two loads Every document and every pointer spends one of two budgets. Most authoring decisions are this one trade made in different places: - **Context load** — what always-loaded material costs the agent's window: an instruction-file line, a skill `description`, anything sitting in context every turn whether or not it fir...