principle-type-system-discipline SKILL.md skillA

This file is byte-identical to the first copy the registry indexed, one of 3 indexed copies. Same content hash, so the same checks give both the same grade.

principle-type-system-discipline from cursor/plugins is an agent skill: a SKILL.md folder an AI agent loads when a task calls for it.

mdr add cursor/plugins/principle-type-system-discipline@git:20261016.182f2ce

Pins git:20261016.182f2ce in mdr.lock. Pin the fingerprint instead.

Audit grade

A, 17 of 17 checks passed

Kind

SKILL.md skill

Repository

cursor/plugins

Path

harness/pstack/claude-code/skills/principle-type-system-discipline/SKILL.md

Versions recorded

1

Latest version

git:20261016.182f2ce, committed Oct 16, 2026

Size

1,557 bytes

Repository stars

13,494

License

none declared

Apply when designing types, reviewing a function signature, or writing code in any statically-typed language. Make illegal states unrepresentable, brand semantic primitives, parse external data at boundaries, exhaust variants, derive from authoritative schemas.

Collected from public GitHub. Every version is saved exactly as it was and never changes. Install it at an exact version with the mdr tool, and every file is checked before it reaches your agent. The main file is checked against the SHA-256 fingerprint recorded here, and the others against the fingerprints GitHub keeps for its source commit. The automatic checks below grade the latest version, and the same checks always give the same file the same grade.

What the file says

# Type System Discipline

Make the compiler reject impossible states, mismatched primitives, and unhandled variants. Prefer defining errors and special cases out of existence over proliferating handlers. For TypeScript syntax, see the `typescript-best-practices` skill.

- **Brand semantic primitives.** `UserId` and `OrderId` are strings underneath but should not be interchangeable. Give each its own type, such as a branded intersection in TypeScript or a newtype elsewhere. Validate once at creation, trust the type downstream. If two arguments share a primitive type but mean different things, brand them.
- **External data is untyped until parsed.** RPC payloads, JSON, IPC messages, CLI args, config files, environment variables, database rows. Have a parse function at every boundary that turns unstructured input into the typed model. The **boundary-discipline** principle skill says where to put validation.
- **Derive types from authoritative schemas.** When a protocol buffer, OpenAPI spec, GraphQL schema, database migration, design-token file, or another file owns a shape, derive from it instead of hand-rolling a parallel type. See the **encode-lessons-in-structure** principle skill.

Read the whole file at its exact version.

How to install

mdr add cursor/plugins/principle-type-system-discipline@sha256:5cdaf79785e3c12b

[![mdr](https://markdownregistry.com/badge/art_6y5hhksujzgyduxo.svg)](https://markdownregistry.com/a/art_6y5hhksujzgyduxo)

Versions

The registry has recorded 1 version of this file, committed on Oct 16, 2026.

Audit of the latest version

Source

API

GET https://markdownregistry.com/api/v1/artifacts/art_6y5hhksujzgyduxo
GET https://markdownregistry.com/api/v1/resolve?ref=cursor/plugins/principle-type-system-discipline
GET https://markdownregistry.com/api/v1/blob/5cdaf79785e3c12b2592b9469ee8c272143eb86ab7a18d8382197cea5fd30106

Your AI assistant does the legwork. You hear about the deals worth your word. Hand yours the standing instructions at modelranch.com and it joins the network that reads files like this one.

Guides: the SKILL.md format and its required fields · what to check before you install a skill · how to pin a skill to an exact version · where to find agent skills · keeping a team on the same skills · which agent file does what.

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