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 backnotprop/pstack is an agent skill: a SKILL.md folder an AI agent loads when a task calls for it.
mdr add backnotprop/pstack/principle-type-system-discipline@git:20261019.6ddf66aPins git:20261019.6ddf66a in mdr.lock. Pin the fingerprint instead.
- Audit grade
- A, 17 of 17 checks passed
- Kind
- SKILL.md skill
- Repository
- backnotprop/pstack
- Path
skills/principle-type-system-discipline/SKILL.md- Versions recorded
- 5
- Latest version
- git:20261019.6ddf66a, committed Oct 19, 2026
- First version recorded
- May 27, 2026
- Size
- 1,557 bytes
- Repository stars
- 3,337
- License
- MIT
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 backnotprop/pstack/principle-type-system-discipline@sha256:5cdaf79785e3c12bThe line at the top of this page pins the label git:20261019.6ddf66a, which is what most people want. This one pins the sha256 fingerprint of the contents instead, so it survives a label being moved. Either way the exact version is written to mdr.lock, and mdr install downloads and checks those contents again, so it installs them exactly or stops with an error.
[](https://markdownregistry.com/a/art_5pr5nlvrhvgi3omw)
2 badge image fetches in 30 days. What the badge shows.
Versions
The registry has recorded 5 versions of this file, between May 27, 2026 and Oct 19, 2026, about one every 36 days.
| version | committed | commit | size | audit | |
|---|---|---|---|---|---|
| git:20261019.6ddf66a latest | 2026-10-19 | 6ddf66a | 1,557 B | A | view · diff |
| git:20261012.f3afb70 | 2026-10-12 | f3afb70 | 3,661 B | A | view · diff |
| git:20260914.55bfdc2 | 2026-09-14 | 55bfdc2 | 4,922 B | A | view · diff |
| git:20260819.4b32d9d | 2026-08-19 | 4b32d9d | 5,097 B | A | view · diff |
| git:20260527.b3eabf1 | 2026-05-27 | b3eabf1 | 3,817 B | A | view |
Audit of the latest version
- pass: Frontmatter block present
- pass: Frontmatter declares a name
- pass: Frontmatter declares a description
- pass: Size between 200 bytes and 200 KB (1557 bytes)
- pass: No zero-width or bidi control characters
- pass: No instruction hidden inside an HTML comment
- pass: No link to an exfiltration or paste host
- pass: No credential-shaped string
- pass: No instruction to send local credentials anywhere
- pass: No text hidden with inline styles
- pass: No prompt-injection phrasing
- pass: No curl or wget piped into a shell
- pass: No recursive delete of root, home or parent
- pass: No instruction to read or print local credentials
- pass: No base64 blob over 200 characters
- pass: No link to a raw IP address
- pass: No script tag
Source
backnotprop/pstack · 3,337 stars · license MIT · pushed 2026-10-28 · branch main
API
GET https://markdownregistry.com/api/v1/artifacts/art_5pr5nlvrhvgi3omw GET https://markdownregistry.com/api/v1/resolve?ref=backnotprop/pstack/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.
More from backnotprop/pstack
Every file in backnotprop/pstack