effect-ontology: Skill for Claude Code

.claude/skills/effect-collections-datastructs/SKILL.md

effect-collections-datastructs is a skill for Claude Code from mepuka/effect-ontology. It costs 37 tokens per session (574 once invoked), scanned A, original, MIT.

A collection of Effect data structures for comparing values by their contents and working with tuples, arrays, chunks, and hash sets. Effect is a TypeScript library for building programs with structured data and pipelines.

In plain words
What is it for?
It is for using Effect's structural equality, tuple and array helpers, Chunk collections, and HashSet collections, with local source references for implementation.
Why use it?
It provides ready-made ways to represent and compare data safely instead of implementing these operations yourself.

Skill for Claude Code

Written for Claude Code: allowed-tools in frontmatter.

This is mepuka/effect-ontology's own configuration. It tells Claude Code how to work on effect-ontology itself, so it is not a mod to install elsewhere. Copy it as a starting point and replace the rules that are about this project. Everything effect-ontology configures →

Reuse

Borrowing it

Nothing to install: this file belongs to mepuka/effect-ontology. Take a copy, put it at the same path in your own repository, and replace the rules that are about this project with yours.

Copy the file
curl -O https://raw.githubusercontent.com/mepuka/effect-ontology/main/.claude/skills/effect-collections-datastructs/SKILL.md
Clone the repo
git clone --depth 1 https://github.com/mepuka/effect-ontology

Made for: Claude Code.

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 effect-collections-datastructs

README.md
[![agentmods](https://agentmods.dev/badge/skills/mepuka/effect-ontology/effect-collections-datastructs.svg)](https://agentmods.dev/skills/mepuka/effect-ontology/effect-collections-datastructs)
Your own site
<a href="https://agentmods.dev/skills/mepuka/effect-ontology/effect-collections-datastructs"><img src="https://agentmods.dev/badge/skills/mepuka/effect-ontology/effect-collections-datastructs.svg" alt="Measured on agentmods" height="20"></a>
Per session 37 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 574 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. A grade says what 26 rules found in the file — not that it is safe.
Origin original 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 $0.00037 $0.00574
Opus 5 $0.00018 $0.00287
Sonnet 5 $0.00007 $0.00115
Haiku 4.5 $0.00004 $0.00057

Measured 8d ago against content hash 3e78bee58f9e, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-08, from the pricing page.

Security

Grade A, and why

effect-collections-datastructs scanned grade A with 0 findings 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 8d 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.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

.claude/skills/effect-collections-datastructs/SKILL.md · 76 lines

What it actually says

Data Structures & Collections

Structural Equality

import { Data, Equal } from "effect"
const a = Data.struct({ id: 1, name: "A" })
const b = Data.struct({ id: 1, name: "A" })
Equal.equals(a, b) // true

Tuples & Arrays

const t = Data.tuple(1, "x")
const arr = Data.array([1,2,3])

Chunk

import { Chunk } from "effect"
const items = Chunk.fromIterable([1,2,3])

HashSet

import { HashSet } from "effect"
const set = HashSet.fromIterable([1,2,3])

Local Source Reference

CRITICAL: Search local Effect source before implementing

The full Effect source code is available at docs/effect-source/. Always search the actual implementation before writing Effect code.

Key Source Files

  • Data: docs/effect-source/effect/src/Data.ts
  • Chunk: docs/effect-source/effect/src/Chunk.ts
  • HashSet: docs/effect-source/effect/src/HashSet.ts
  • Equal: docs/effect-source/effect/src/Equal.ts

Example Searches

# Find Data.struct and equality patterns
grep -F "Data.struct" docs/effect-source/effect/src/Data.ts
grep -F "Data.tuple" docs/effect-source/effect/src/Data.ts

# Find Chunk operations
grep -F "export" docs/effect-source/effect/src/Chunk.ts | grep -F "function"

# Study HashSet API
grep -F "export" docs/effect-source/effect/src/HashSet.ts | grep -F "function"

# Find Equal implementation
grep -F "equals" docs/effect-source/effect/src/Equal.ts

Workflow

  1. Identify the collection API you need (e.g., Chunk, HashSet)
  2. Search docs/effect-source/effect/src/ for the implementation
  3. Study the types and available operations
  4. Look at test files for usage examples
  5. Write your code based on real implementations

Real source code > documentation > assumptions

References

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. 8d ago First seen · 76 lines · 37 tokens per session scan A 3e78bee58f9e

Subscribe to this mod's changes

effect-collections-datastructs is a skill published in the GitHub repository mepuka/effect-ontology (5 stars, last pushed 8mo ago), licensed MIT. It adds 37 tokens to every session and 574 once invoked, about $0.0002 per session on Opus 5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-31.

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