# Principle Boundary Discipline

> Concentrate parsing, validation, and error translation at real system boundaries while keeping typed internal business logic small and direct.

- Skill: `njs14/principle-boundary-discipline` (Agent Skill)
- Install (CLI): `npx skillmds@latest add njs14/principle-boundary-discipline`
- Raw SKILL.md: https://api.skillmd.com/api/skills/njs14/principle-boundary-discipline/raw
- Safety review: pending
- Works with: Claude Code, Claude.ai, OpenAI Codex
- Category: Coding & Dev Tools
- Author: njs14 (https://skillmd.com/u/njs14)
- Updated: 2026-09-17
- Page: https://skillmd.com/skills/njs14/principle-boundary-discipline

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# Keep guards at boundaries

Treat the request text that activated this skill as the boundary decision to inspect.

Apply [boundary discipline](../pkstack-principles/references/catalog.md#boundary-discipline). Identify the
exact CLI, file, configuration, network, database, or external API crossing. Parse once into a
domain value, translate errors there, and remove redundant internal guards only when the parsed
type truly carries the invariant. Return the boundary, the trusted internal shape, and its focused
test.