effect

A reference guide for answering questions about Effect, a TypeScript framework for building programs with structured handling of effects such as errors and asynchronous work.

In plain words
What is it for?
Investigating Effect APIs and programming patterns in its source repository, then using those verified findings to answer technical questions.
Why use it?
It requires answers to be checked against the framework’s source code and documentation rather than relying on memory.

Skill for Claude CodeCodex

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.

agentmods
npx agentmods add skills/xiaomimimo/mimo-code/effect
Any agent
npx skills add XiaomiMiMo/MiMo-Code --skill effect
Clone the repo
git clone --depth 1 https://github.com/XiaomiMiMo/MiMo-Code

Made for: Claude Code, Codex.

Per session 8 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 161 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
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 $0.00008 $0.00161
Opus 5 $0.00004 $0.00081
Sonnet 5 $0.00002 $0.00032
Haiku 4.5 $0.00001 $0.00016

Measured yesterday against content hash 0a47f9b87995, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

effect 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 yesterday.

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.

.mimocode/skills/effect/SKILL.md · 22 lines

What it actually says

Effect

This codebase uses Effect, a framework for writing typescript.

How to Answer Effect Questions

  1. Clone the Effect repository: https://github.com/Effect-TS/effect-smol to .opencode/references/effect-smol in this project NOT the skill folder.
  2. Use the explore agent to search the codebase for answers about Effect patterns, APIs, and concepts
  3. Provide responses based on the actual Effect source code and documentation

Guidelines

  • Always use the explore agent with the cloned repository when answering Effect-related questions
  • Reference specific files and patterns found in the Effect codebase
  • Do not answer from memory - always verify against the source
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. yesterday First seen · 22 lines · 8 tokens per session scan A 0a47f9b87995

Subscribe to this mod's changes

effect is a skill published in the GitHub repository XiaomiMiMo/MiMo-Code (12,904 stars, last pushed 2d ago), licensed MIT. It adds 8 tokens to every session and 161 once invoked, about $0.0000 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 2026-08-30.

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