Rule writing

<!-- cloud_safe: degrade -->

rule-writing

When to use

• Creating a new rule in src/rules/{name}.md
• Rewriting an existing rule (not a typo fix)
• Deciding whether something should be a rule at all
• Converting a learning from learning-to-rule-or-skill into a concrete rule

Do NOT use this skill when:

• The content is a multi-step workflow → use skill-writing
• The content is reference material agents cite → use guideline-writing
• The content is a user-invoked action → use command-writing

Rule vs skill vs guideline — critical test

Intent	Artifact
"Agent must always/never do X"	Rule
"When Y happens, run these steps"	Skill
"Here is knowledge the agent may cite"	Guideline

A rule is a constraint — it states a boundary, not a workflow. If the content needs numbered steps, it is a skill.

Procedure

0. Run the Drafting Protocol

Creating or materially rewriting a rule must go through Understand → Research → Draft from the artifact-drafting-protocol rule.

• Understand — which agent behavior is wrong today? What should change? Can you point to a concrete incident or repeated pattern?
• Research — inspect src/rules/ for overlap and analyze rule-type-governance, size-enforcement, skill-quality before drafting.
• Draft — propose frontmatter (type, description) first, wait for confirmation, then fill the body.

1. Classify type — always vs auto

Normative source: rule-type-governance.

• always — universal behavior (language, scope, safety, verification)
• auto — triggered by description match on domain/symptom

Default to auto. always must be justified — if >50% of conversations don't need it, it is auto.

2. Write a trigger-style description

The description field is the trigger. Describe when the rule applies, not what it contains. Soft cap: 200 characters.

# Bad — describes content, won't match reliably:
description: "PHP coding standards"

# Good — trigger-shaped, names domain + symptoms:
description: "Writing or reviewing PHP code — strict types, naming, comparisons, early returns, Eloquent conventions"

When iterating on phrasing, delegate to the description-assist skill — approval-gated, no silent edits, max two rounds.

3. Write the rule body

• Short, constraint-only, easy to scan.
• Bullet lists, tables, do/don't blocks — not paragraphs of prose.
• No numbered procedures — if you need steps, it is a skill.
• Link out to guidelines for deep reference instead of inlining them.

3b. Path conventions in frontmatter and body — load-bearing

Three different surfaces, three different rules. Mixing them up will either fail the schema (./scripts-run src/scripts/validate_frontmatter) or fail ./scripts-run src/scripts/lint_load_context. Canonical reference: templates/rule.md § Path conventions and docs/contracts/load-context-schema.md.

Field	Form	Example
load_context: / load_context_eager:	Logical name rooted at the source — never src/	contexts/execution/verification-mechanics.md
triggers[].path_prefix:	Literal match pattern the host evaluates against the file the agent is editing — not rewritten	src/skills/ (source-of-truth rules) or agents/, app/, .augment/
Body links to guidelines / contracts	Verbatim relative form — ../../docs/... works in any markdown viewer; rewriter handles depth	[guideline](../../docs/guidelines/<group>/<name>.md)

The condense-time rewriter (scripts/condense.ts::_rewrite_paths) is idempotent and depth-aware — it resolves logical names and body links to the deployment-correct relative path at condense time, leaving path_prefix: literally as written. The schema regex (scripts/schemas/rule.schema.json) and scripts/lint_load_context.ts both reject the src/ prefix in load_context: / load_context_eager: with an error pointing at the canonical logical name.

4. Enforce the size budget

Normative source: size-enforcement + docs/guidelines/agent-infra/size-and-scope.md.

Category	Target
Ideal	< 60 non-empty lines
Acceptable	< 100–120 lines
Hard limit	< 200 lines

Linter emits long_rule above ~80 non-empty lines. Above that, justify in the PR or split by responsibility.

5. Validate

• Run ./scripts-run src/scripts/skill_linter src/rules/{name}.md → must report 0 FAIL.
• Run bash scripts/condense.sh --sync to regenerate dist/agent-src/rules/{name}.md.
• Run ./scripts-run src/scripts/condense --generate-tools to project into .claude/, .cursor/, .clinerules/, .windsurfrules.
• Run the full CI pipeline locally (see Taskfile.yml in this repo for the script list) — must exit 0 except for tolerated warnings.

5b. Budget-discipline gate — hard stop

After validation, before declaring the rule done, run:

./scripts-run src/scripts/measure_augment_budget --check

If utilisation is ≥ 0.95 (or the check exits non-zero), STOP and invoke rule-refactor. Do NOT:

• Trim the new rule further to "just fit" — if it needs that body to do its job, the rule is right and the rule set around it is wrong.
• Raise FAIL_THRESHOLD in scripts/measure_augment_budget.ts — threshold-lift is explicitly forbidden (see the validation-budget rule and the rule-refactor Iron Law).
• Promote an always-rule to auto to dodge the cap if the rule's semantics require always-on visibility — that breaks the rule, not the budget.

The discipline: budget pressure is the signal that the rule set needs a cleanup pass, not that the new rule needs to be smaller. The rule-refactor skill runs the audit and proposes merge / delete / move-to-context / promote-to-skill so the new rule earns its space.

6. Governance baseline (when introducing a new linter check)

Advisory, reviewer-checked — no CI gate. When the same PR adds a new check to scripts/skill_linter.ts (or strengthens an existing one) such that previously-clean rules now warn, the PR body MUST record the pre-existing violations on main in a Markdown table:

### Pre-existing baseline (informational)

| Code | Count on main | Bucket |
|---|---:|---|
| {new_code} | N | (a) genuine fix · (b) accept · (c) check too aggressive |

Forward-only: the new check applies to the rule under review and to future edits. The baseline table is informational so reviewers can distinguish genuine debt from acceptable carry-overs without diffing the full lint output. See agents/evidence/analysis/lint-warning-triage.md for the 3-bucket reference.

Frontmatter shape

---
type: "auto"              # or "always"
description: "Trigger-shaped sentence — domain + symptoms — soft cap 200 chars"
alwaysApply: false        # true only if type: always
source: package           # or project for consumer-local rules
load_context:             # logical names only — `contexts/<area>/<file>.md`
  - contexts/execution/verification-mechanics.md
triggers:                 # path_prefix is literal, not rewritten
  - path_prefix: "src/rules/"
routes_to:
  - "skill:related-skill"
---

See § 3b above for the load-bearing distinction between load_context: (logical, rewritten), triggers[].path_prefix: (literal, verbatim), and body links (relative ../../docs/..., rewriter handles depth).

Output format

1. Complete rule file at src/rules/{name}.md
2. Frontmatter fully populated, no placeholders left
3. Linter output showing 0 FAIL
4. Confirmation that bash scripts/condense.sh --sync + ./scripts-run src/scripts/condense --generate-tools ran clean

Gotchas

• Writing a rule that duplicates an existing one — always grep first.
• Defaulting to always "just in case" — token cost is real, auto is default.
• Description like "Rule about X" — it must describe when, not what.
• Pasting a workflow into a rule — if it has numbered steps, split into a skill.
• Forgetting to run ./scripts-run src/scripts/condense --generate-tools — downstream tools stay stale.
• Editing dist/agent-src/rules/ or .augment/rules/ directly — those are generated.

Frugality Standards

Apply the Frugality Charter to every rule you author.

Examples in this artifact:

• Per the charter's default-terse rule, no intent prose in the rule body — start with the obligation, not a setup paragraph.
• Per the Iron-Law literal predicate, ALL-CAPS fenced obligations belong only when the rule sits on the kernel-membership list.
• Per the cheap-question check, the rule's "When to ask" guidance must list decidable triggers, not vibe-based judgment.

Pre-save self-check:

1. Does the rule body open with the obligation, or with a setup paragraph?
2. Are any examples mere narration (no decidable test)?
3. Are ALL-CAPS Iron-Law blocks used outside a kernel-listed rule?
4. Are interactions duplicated from another rule rather than linked?

Do NOT

• Do NOT inline long procedures
• Do NOT exceed the hard size limit without an explicit waiver
• Do NOT edit projections (dist/agent-src/, .augment/, .claude/, etc.)
• Do NOT skip the linter
• Do NOT create a rule when a guideline or skill is the right shape

Cloud Behavior

On cloud surfaces (Claude.ai Web, Skills API) the package's scripts/skill_linter.ts, scripts/condense.ts, and task runner are not reachable. The skill still applies — with prose-only validation:

• Emit the full rule file as a copyable Markdown block. Do not attempt to write to disk.
• Self-check the frontmatter against the rules: type is always or auto, description is trigger-shaped, alwaysApply matches type.
• Self-check the body: under the size budget (200 lines hard, 120 soft), trigger sentence first, no embedded procedures.
• Tell the user to save under src/rules/{name}.md and run task sync && task lint-skills locally before committing.
• Do not call the linter or condenseor — they only run on the user's machine.

Examples

Good description (trigger-shaped, names domain + symptoms):

"Git commit message format, branch naming, conventional commits, committing, pushing, or creating pull requests"

Bad description (no trigger, too vague):

"Commit conventions"