functional-core-imperative-shell SKILL.md skillA
functional-core-imperative-shell from ed3dai/ed3d-plugins is an agent skill: a SKILL.md folder an AI agent loads when a task calls for it.
mdr add ed3dai/ed3d-plugins/functional-core-imperative-shell@git:20260218.0673566Pins git:20260218.0673566 in mdr.lock. Pin the fingerprint instead.
- Audit grade
- A, 17 of 17 checks passed
- Kind
- SKILL.md skill
- Repository
- ed3dai/ed3d-plugins
- Path
plugins/ed3d-house-style/skills/howto-functional-vs-imperative/SKILL.md- Versions recorded
- 3
- Latest version
- git:20260218.0673566, committed Feb 18, 2026
- First version recorded
- Jan 15, 2026
- Size
- 13,703 bytes
- Repository stars
- 253
- License
- none declared
Use when writing or refactoring code, before creating files - enforces separation of pure business logic (Functional Core) from side effects (Imperative Shell) using FCIS pattern with mandatory file classification.
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
# Functional Core, Imperative Shell (FCIS) ## Overview **Core principle:** Separate pure business logic (Functional Core) from side effects (Imperative Shell). Pure functions go in one file, I/O operations in another. **Why this matters:** Pure functions are trivial to test (no mocks needed). I/O code is isolated to thin shells. Bugs become structurally impossible when business logic has no side effects. ## When to Use **Use FCIS when:** - Writing any new code file - Refactoring existing code - Reviewing code for architectural decisions - Deciding where logic belongs **Trigger symptoms:** - "Where should this function go?" - Creating a new file - Adding database calls to logic - Adding file I/O to calculations - Writing tests that need complex mocking ## MANDATORY: File Classification **YOU MUST add pattern comment to every file containing runtime behavior:** ``` // pattern: Functional Core // pattern: Imperative Shell // pattern: Mixed (needs refactoring) ``` **If file genuinely cannot be separated (rare), document why:** ``` // pattern: Mixed (unavoidable) // Reason: [specific technical justification] …
Read the whole file at its exact version.
How to install
mdr add ed3dai/ed3d-plugins/functional-core-imperative-shell@sha256:ac1000351b2dcee5The line at the top of this page pins the label git:20260218.0673566, 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_eii6dxuhhndb4ls7)
3 badge image fetches in 30 days. What the badge shows.
Versions
The registry has recorded 3 versions of this file, between Jan 15, 2026 and Feb 18, 2026, about one every 17 days.
| version | committed | commit | size | audit | |
|---|---|---|---|---|---|
| git:20260218.0673566 latest | 2026-02-18 | 0673566 | 13,703 B | A | view · diff |
| git:20260204.611bfd1 | 2026-02-04 | 611bfd1 | 12,935 B | A | view · diff |
| git:20260115.cf17c55 | 2026-01-15 | cf17c55 | 12,913 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 (13703 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
ed3dai/ed3d-plugins · 253 stars · license none declared · pushed 2026-09-06 · branch main
API
GET https://markdownregistry.com/api/v1/artifacts/art_eii6dxuhhndb4ls7 GET https://markdownregistry.com/api/v1/resolve?ref=ed3dai/ed3d-plugins/functional-core-imperative-shell GET https://markdownregistry.com/api/v1/blob/ac1000351b2dcee58c0910d462767309c9f466c5b0e05ef9479ad34a69ad50c6
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.