principle-type-system-discipline SKILL.md skillA

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

mdr add nightly-labs/openbot/principle-type-system-discipline@git:20261013.9e6954c

Pins git:20261013.9e6954c in mdr.lock. Pin the fingerprint instead.

Audit grade

A, 17 of 17 checks passed

Kind

SKILL.md skill

Repository

nightly-labs/openbot

Path

marketplace/production-catalog/bundles/pstack/skills/principle-type-system-discipline/SKILL.md

Versions recorded

1

Latest version

git:20261013.9e6954c, committed Oct 13, 2026

Size

3,661 bytes

Repository stars

5,267

License

a license file GitHub does not identify

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, refuse to lie to the compiler, 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.

- **Make illegal states unrepresentable.** Model variants as sum types (discriminated unions, enums with payloads, sealed classes), not as a bag of optional fields where contradictory combinations compile. `{ completed: boolean; completedAt?: Date }` admits `completed: true` with no date. Derive the boolean from `completedAt`, or model `{ kind: 'open' } | { kind: 'done'; at: Date }`. If you can write a comment explaining when a combination of fields is valid, split it into a sum type.
- **Types are constructions, not restrictions.** Build the type up from the values you want instead of carving them out of a looser type with checks. A non-empty list is a head plus a rest. A valid time range is a start plus a duration. Choose the shape that cannot build the illegal value and expose the interface callers need on top.
…

Read the whole file at its exact version.

How to install

mdr add nightly-labs/openbot/principle-type-system-discipline@sha256:2e492cef34bb25a2

[![mdr](https://markdownregistry.com/badge/art_iyhkpxwuwhf7udoc.svg)](https://markdownregistry.com/a/art_iyhkpxwuwhf7udoc)

Versions

The registry has recorded 1 version of this file, committed on Oct 13, 2026.

Audit of the latest version

Source

API

GET https://markdownregistry.com/api/v1/artifacts/art_iyhkpxwuwhf7udoc
GET https://markdownregistry.com/api/v1/resolve?ref=nightly-labs/openbot/principle-type-system-discipline
GET https://markdownregistry.com/api/v1/blob/2e492cef34bb25a20b9115df61f9ef3a9837e3fda144ffda8079e5f45a1b72e8

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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