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.
curl -O https://raw.githubusercontent.com/mepuka/effect-ontology/main/.claude/skills/effect-collections-datastructs/SKILL.mdgit clone --depth 1 https://github.com/mepuka/effect-ontologyWrote 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.
[](https://agentmods.dev/skills/mepuka/effect-ontology/effect-collections-datastructs)<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>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.
| Model | Per session | Once 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 |
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.
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
- Identify the collection API you need (e.g., Chunk, HashSet)
- Search
docs/effect-source/effect/src/for the implementation - Study the types and available operations
- Look at test files for usage examples
- Write your code based on real implementations
Real source code > documentation > assumptions
References
- Agent Skills overview: https://www.anthropic.com/news/skills
- Skills guide: https://docs.claude.com/en/docs/claude-code/skills
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.
- 8d ago First seen · 76 lines · 37 tokens per session scan A 3e78bee58f9e
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.
Other skills, from other repositories
no-bare-casts
Writing as in TypeScript or TSX production code, modifying a file that contains a bare as cast, silencing a type error with a cast, encountering as unknown as, or reviewing a cast site.
aws-sst-development
SST v4 (Ion) expert for managing AWS resources as code with the Pulumi-backed framework.
league-akari-shard-development
Use when creating, extending, refactoring, splitting, or reviewing League Akari main or renderer shards, including shard file organization, controller/loader/executor/handler boundaries, naming conventions, renderer TSX usage, platform guards, and public contract compatibility.
fast-typescript-check
Keep www-sacred's TypeScript fast to type-check and fast to run. Use when touching the ASCII/canvas animation components (the only real per-frame code here), tightening type-check wall-clock, or auditing a change for runtime or compiler regressions. Scoped to this repo — a React 19 / Next.js 16 component library plus…
dd-code-generation
Use pup CLI for immediate Datadog operations or generate code for integration into applications.
migrate-better-result-3
Migrate a TypeScript codebase from better-result 2.x to 3.0. Use when upgrading better-result across the TaggedError syntax, removed Result serialization helpers, recovery inference, matching, or retry APIs.