functional-core-imperative-shell

functional-core-imperative-shell is a skill for Claude Code from ed3dai/ed3d-plugins. It costs 46 tokens per session (3,133 once invoked), scanned A, original, no licence file.

A coding pattern that keeps pure business rules separate from side effects such as file access, network calls, or database changes.

In plain words
What is it for?
Use it before creating or changing files to classify code and structure or refactor it using the Functional Core, Imperative Shell pattern.
Why use it?
It makes code boundaries clearer and reduces the chance that external actions become tangled with business logic.

Skill for Claude Code

Written for Claude Code: user-invocable in frontmatter.

Part of the ed3d-house-style plugin — 10 skills shipped together

Good fit Use it before creating or changing files to classify code and structure…

Compare 6 skills from other repositories ↓
Install with agentmods
npx agentmods add skills/ed3dai/ed3d-plugins/howto-functional-vs-imperative
Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

Any agent
npx skills add ed3dai/ed3d-plugins --skill howto-functional-vs-imperative
Clone the repo
git clone --depth 1 https://github.com/ed3dai/ed3d-plugins

Made for: Claude Code.

Or install ed3d-house-style, the plugin that ships this one along with the rest of its 10 skills.

Wrote this? Show the measurements

A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.

agentmods badge for functional-core-imperative-shell

README.md
[![agentmods](https://agentmods.dev/badge/skills/ed3dai/ed3d-plugins/howto-functional-vs-imperative.svg)](https://agentmods.dev/skills/ed3dai/ed3d-plugins/howto-functional-vs-imperative)
Your own site
<a href="https://agentmods.dev/skills/ed3dai/ed3d-plugins/howto-functional-vs-imperative"><img src="https://agentmods.dev/badge/skills/ed3dai/ed3d-plugins/howto-functional-vs-imperative.svg" alt="Measured on agentmods" height="20"></a>
Per session 46 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 3,133 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 1 finding. A grade says what 26 rules found in the file — not that it is safe.
Origin unknown No closer match found in the catalogue.
Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

ModelPer sessionOnce invoked
Fable 5.1 $0.00046 $0.03133
Opus 5 $0.00023 $0.01566
Sonnet 5 $0.00009 $0.00627
Haiku 4.5 $0.00005 $0.00313

Measured 7d ago against content hash ac1000351b2d, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-06, from the pricing page.

Security

Grade A, and why

functional-core-imperative-shell scanned grade A with 1 finding against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 7d ago.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Makes network callslowCapability

Not a fault in itself. Listed so you know the mod talks to something, and to what.

order = db.fetch(order_id) # I/O
plugins/ed3d-house-style/skills/howto-functional-vs-imperative/SKILL.md · 376 lines

The source is not reproduced here

No licence file

A repository with no LICENSE is all rights reserved by default, so the body is not copied here. The metadata, the measurements and the link are.

Read it on GitHub

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

  1. 7d ago First seen · 376 lines · 46 tokens per session scan A ac1000351b2d

Subscribe to this mod's changes

functional-core-imperative-shell is a skill published in the GitHub repository ed3dai/ed3d-plugins (249 stars, last pushed 2mo ago), with no licence file. It adds 46 tokens to every session and 3,133 once invoked, about $0.0002 per session on Opus 5. A static security scan graded it A with 1 finding (makes network calls). No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.