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Agent skill

Effect V4

by ComposioHQ in ComposioHQ/composio

Write, review, or upgrade Effect v4 code in the Composio CLI, cli-keyring, and json-schema-to-effect-schema packages, all pinned exactly to effect@4.0.0-rc.117 — Context.Service and explicit layers…

MITAuto-check passedProductivity & Automation

Install Effect V4

skills CLI
$ npx skills add ComposioHQ/composio --skill effect-v4 -a claude-code

Project install by default; add -g for ~/.claude/skills/.

GitHub CLI
$ gh skill install ComposioHQ/composio effect-v4 --agent claude-code

Project scope by default; add --scope user for a personal install. Needs GitHub CLI 2.90.0 or later (public preview).

Manual copy
$ git clone --depth 1 https://github.com/ComposioHQ/composio.git skills-src && mkdir -p .claude/skills && cp -r skills-src/.agents/skills/effect-v4 .claude/skills/effect-v4 && rm -rf skills-src

Use ~/.claude/skills/ instead of .claude/skills for a personal install. The folder must contain SKILL.md.

Claude Code skills documentation · loads skills from .claude/skills/

Facts

Skill name
effect-v4
GitHub stars
30k
Token cost
~1k tokens
SKILL.md length
387 words
Files
6 (incl. scripts, references)
Skills in repo
7
Repo updated
First seen
Licence
MIT

At a glance

Write, review, or upgrade Effect v4 code in the Composio CLI, cli-keyring, and json-schema-to-effect-schema packages, all pinned exactly to effect@4.0.0-rc.117 — Context.Service and explicit layers…

  • Reviewing Effect v4 code
  • SKILL.md covers Exact version matrix, Read next, Non-negotiables and Verification
  • Runs JavaScript scripts from its folder; calls pnpm and node
  • Answering a v4 API question

What it does

Effect V4 is an agent skill from ComposioHQ/composio. Write, review, or upgrade Effect v4 code in the Composio CLI, cli-keyring, and json-schema-to-effect-schema packages, all pinned exactly to effect@4.0.0-rc.117 — Context.Service and explicit layers, Schema.TaggedError and typed recovery, the effect/unstable/cli command surface, and the vendored effect source oracle. Use when writing or reviewing Effect v4 code, answering a v4 API question, working in effect/unstable/cli, defining a Context.Service service, modeling an error with Schema.TaggedError, bumping the…

Its SKILL.md is about 1k tokens, which your agent loads only when the skill is triggered. The skill folder holds 7 other files, including scripts and reference files (for example `references/cli-surface.md`, `references/core-patterns.md` and `references/upgrade-workflow.md`).

It sits in Productivity & Automation, covering App automation through connectors and End-to-end testing. It works with Composio, Model Context Protocol and TypeScript. The repository describes itself as: Composio powers 1000+ toolkits, tool search, context management, authentication, and a sandboxed workbench to help you build AI agents that turn intent into action. The licence is MIT.

When your agent uses it

  • Reviewing Effect v4 code
  • Answering a v4 API question
  • Working in effect/unstable/cli
  • Defining a Context.Service service

Example prompts

  • “/effect-v4”

Requirements

  • Node.js

What it can do on your machine

Read from SKILL.md and the folder at commit f6f9667. It shows what the files ask for, not the result of running them.

  • Tool permissions

    Pre-approves nothing: there is no allowed-tools line, so your agent's usual permission prompts apply.

    From allowed-tools in the SKILL.md frontmatter.

  • Runs code

    Ships 1 file in scripts/ (JavaScript), which the agent can run.

    Shell commands in SKILL.md call:

    • pnpm
    • node

    From the folder's file list and the shell code blocks in SKILL.md.

  • Network

    No URLs in SKILL.md. Its commands use pnpm, which can reach the network depending on how they are called.

    From URLs in SKILL.md, links to its own repository left out.

  • Credentials

    Names no API keys, tokens, secrets or passwords.

    From names ending in _API_KEY, _TOKEN, _SECRET, _KEY or _PASSWORD in SKILL.md.

Context cost

Effect V4 loads about 1k tokens when it runs, and up to ~7k if it reads all its reference files. Until then it costs about 175 tokens; SKILL.md has 387 words of instructions outside code blocks.

Always · name and description, kept in context so the agent knows when to use it
~175
When it runs · the whole SKILL.md, loaded when a task matches
~1k
With references · SKILL.md plus every file in references/, read only if the agent opens them
~7k

Estimates: characters ÷ 4, the usual rule of thumb; real counts depend on the model's tokenizer. Scripts and assets cost tokens only if the agent reads them.

Safety

Auto-check passed

The automated check found no risky patterns in SKILL.md.

Automated static check — not a guarantee. Review scripts before installing. It scans the text of SKILL.md for risky patterns (piping downloads into a shell, reading credential files, hidden Unicode, destructive commands); the scripts in this folder are not scanned.

SKILL.md

The full file from ComposioHQ/composio at commit f6f9667, republished under its MIT licence (© ComposioHQ). 387 words, ~1,047 tokens.

Download SKILL.mdSave it as .claude/skills/effect-v4/SKILL.md (or your agent's skills folder). This skill also uses 5 other files; get the full folder from GitHub.
name
effect-v4
description
Write, review, or upgrade Effect v4 code in the Composio CLI, cli-keyring, and json-schema-to-effect-schema packages, all pinned exactly to effect@4.0.0-rc.117 — Context.Service and explicit layers, Schema.TaggedError and typed recovery, the effect/unstable/cli command surface, and the vendored effect source oracle. Use when writing or reviewing Effect v4 code, answering a v4 API question, working in effect/unstable/cli, defining a Context.Service service, modeling an error with Schema.TaggedError, bumping the Effect prerelease pins, or verifying an unfamiliar API against ts/vendor/effect. Do not use for CLI command UX/wiring design (use cli-command) or CLI E2E tests (use cli-e2e).

Effect v4

The CLI, @composio/cli-keyring, and @composio/json-schema-to-effect-schema run on Effect v4 (release candidate). Every claim below is grounded in the migrated source, not memory of v3.

Exact version matrix

effect, @effect/platform-bun, and @effect/vitest are pinned to the same exact 4.0.0-rc.117 — never ^, @next, or a mismatched prerelease across packages. @effect/cli and @effect/platform no longer exist as dependencies; their surfaces are consolidated into effect and effect/unstable/*. See versions.json for the full matrix (also typescript, vitest).

  • references/core-patterns.md — services, layers, typed errors, Schema, choosing between Effect.gen and Effect.fn, and the v3→v4 rename table (labeled historical, for recognizing stale patterns).
  • references/cli-surface.md — effect/unstable/cli: Command, Flag, Argument, GlobalFlag, CliConfig, the custom CliOutput.Formatter, and the runner's double-print rule.
  • references/upgrade-workflow.md — procedure for bumping to a newer prerelease.

Code excerpts in those references are short quotes from real, currently-compiling repo files (path cited at each excerpt) — not standalone examples. The compile-checked source of truth is always the cited file itself; when it and a reference disagree, trust the file and fix the reference.

Non-negotiables

  • Effect.gen(function* () {...}) for effect values — the dominant form, including named module consts — and (params) => Effect.gen(...) for parameterized helpers. Effect.fn(...) is the function form whose effects carry stack-frame annotations (its optional name string adds a per-call tracing span), worth it for service members and combinator callbacks that should be attributable in error reports. All forms re-run their body per execution. See "Effect.gen vs Effect.fn" in core-patterns.
  • Define services with Context.Service and an explicit static readonly Default/layer layer built with Layer.succeed/Layer.effect/Layer.provide. V4 does not generate a layer for you.
  • Model expected failures with Schema.TaggedError (or a plain Data.TaggedError when no Schema fields are needed) and recover with Effect.catchTag/catchTags/Match, never manual _tag string comparisons.
  • Wrap fallible Promises with Effect.tryPromise({ try, catch }); Effect.promise turns rejection into a defect. No async/await or try/catch inside Effect workflows — ESLint bans them in ts/packages/cli/src.
  • Treat every remembered v3 package name and API as wrong until verified against ts/vendor/effect (read-only source oracle — never edit or import from it) and the installed effect@4.0.0-rc.117 typings. Source may be ahead of the published package; the compiler is the compatibility gate.
Show full SKILL.md (44 more words)Show less

Verification

bash
pnpm typecheck
pnpm --filter @composio/cli test

Run pnpm validate:agent-skills and pnpm validate:skill-routing after editing this skill or its descriptions, and compile the TypeScript blocks in this skill and in typescript-testing/references/effect-v4-cli.md against the pinned packages with:

bash
node .agents/skills/effect-v4/scripts/check-examples.mjs

Blocks that quote repo files with unresolvable imports carry a no-check fence info string.

© ComposioHQ, MIT. Rendered from Markdown: HTML in the file is shown as text, images as links, and headings moved down two levels. Raw file

Files

SKILL.md and 5 other files (scripts, references) in .agents/skills/effect-v4 of ComposioHQ/composio.

  • SKILL.md
  • references/cli-surface.md
  • references/core-patterns.md
  • references/upgrade-workflow.md
  • scripts/check-examples.mjs
  • versions.json

Open the folder on GitHubat commit f6f9667

Compare with similar skills

Effect V4 next to the 5 skills that share the most tags, products or categories with it. Stars are the repository's; “used in” counts other GitHub owners with a copy.

Effect V4 compared with similar skills
SkillStarsUsed inTokensAuto-checkLicenceRepo updated
Effect V4 this skillComposioHQ/composio30k—~1kAutomated safety check: PassMIT
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Reddit Post EngineVarnan-Tech/opendirectory674—~3.2kAutomated safety check: NotesMIT
Accelo Automation via Rube MCPComposioHQ/awesome-claude-skills77k3 repos~727Automated safety check: PassNone
Manual Testhypequery/hypequery103—~618Automated safety check: PassCustom licence
Acculynx Automation via Rube MCPComposioHQ/awesome-claude-skills77k3 repos~734Automated safety check: PassNone

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Works with

Categories

Questions about Effect V4

What does Effect V4 do?

Write, review, or upgrade Effect v4 code in the Composio CLI, cli-keyring, and json-schema-to-effect-schema packages, all pinned exactly to effect@4.0.0-rc.117 — Context.Service and explicit layers…. Effect V4 is an agent skill from ComposioHQ/composio.TaggedError and typed recovery, the effect/unstable/cli command surface, and the vendored effect source oracle.

When should I use Effect V4?

Effect V4 fits situations like: reviewing Effect v4 code; answering a v4 API question; working in effect/unstable/cli; defining a Context.Service service.

How do I install Effect V4 in Claude Code?

Run `npx skills add ComposioHQ/composio --skill effect-v4 -a claude-code`. Or copy the skill folder (.agents/skills/effect-v4 in ComposioHQ/composio) into .claude/skills/effect-v4 in your project. Claude Code loads it when a task matches its description.

How do I install Effect V4 in Codex?

Run `npx skills add ComposioHQ/composio --skill effect-v4 -a codex`. Or copy the skill folder (.agents/skills/effect-v4 in ComposioHQ/composio) into .agents/skills/effect-v4 in your project. Codex loads it when a task matches its description.

Can I use Effect V4 in Cursor, Gemini CLI or GitHub Copilot?

Cursor, Gemini CLI, GitHub Copilot and OpenCode also load SKILL.md folders. With the skills CLI, run `npx skills add ComposioHQ/composio --skill effect-v4 -a cursor` (or -a gemini-cli, github-copilot or opencode for the others). To copy it by hand, put the folder in .cursor/skills/effect-v4, .gemini/skills/effect-v4, .github/skills/effect-v4 and .opencode/skills/effect-v4 in your project.

What does Effect V4 need to run?

Going by SKILL.md and its folder, Effect V4 needs JavaScript for the scripts in its folder and the command-line tools its instructions call (pnpm and node). Our summary lists: Node.js.

Does Effect V4 access the network?

SKILL.md contains no URLs. Any network use would come from the scripts or tools the agent runs. This is read from the text; nothing was executed.

Is Effect V4 safe to install?

Our automated static check of SKILL.md found no risky patterns, such as piping downloads into a shell, reading credential files or hidden Unicode. It is not a guarantee. The check reads SKILL.md only: the scripts in the folder are not scanned, so read them before running anything.

What licence does Effect V4 use?

Effect V4 is published under the MIT licence (the repository's licence). It allows redistribution, so the full SKILL.md is shown on this page.

How many tokens does Effect V4 use?

About 1k tokens (SKILL.md is roughly 4.2k characters). Agents keep only the skill's name and description in context until a task matches; then they load SKILL.md in full. Its references folder adds about 5.9k tokens, read only when the agent opens those files.

What are the alternatives to Effect V4?

Skills that share tags, products or a category with Effect V4: Composio Byo (drewnekota/cetus, 146 stars), Reddit Post Engine (Varnan-Tech/opendirectory, 674 stars), Accelo Automation via Rube MCP (ComposioHQ/awesome-claude-skills, 77k stars) and Manual Test (hypequery/hypequery, 103 stars). The comparison table on this page puts their stars, adoption, token cost, safety result and licence side by side.

Who maintains Effect V4?

ComposioHQ (a GitHub organization) maintains it in ComposioHQ/composio, which has 30,467 GitHub stars. The repository holds 7 skills in this directory. The repository was last updated on October 8, 2026.

Source: ComposioHQ/composio on GitHub. Facts on this page come from the repository at the commit we read; the author's words are quoted as theirs.