# Principle Type System Discipline

> Make invalid states hard or impossible to represent and parse external primitives into meaningful internal types at the edge. Use at data modeling, API design, or external data ingestion points.

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

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# Type System Discipline

## Trigger

At data modeling, API design, or external data ingestion points.

## Rule

Make invalid states hard or impossible to represent and parse external primitives into meaningful internal types at the edge.

## Application

1. Name the concrete decision this principle changes.
2. Apply the rule to that decision, not as a decorative citation.
3. Prefer evidence from the current repository/runtime over generic preference.
4. If the principle conflicts with an explicit user constraint, keep the constraint and state the tradeoff.