Guidance for Effect, a TypeScript library for building programs with explicit error handling, dependencies, resource cleanup, data validation, and other structured workflows.

Use it when working on TypeScript applications that use Effect features such as services, dependency wiring, resource lifecycles, schemas, tests, streams, or AI-related modules.

It helps developers choose consistent ways to represent expected errors, connect program dependencies, manage resources, and run Effect-based code. It is intended for building, changing, reviewing, or explaining Effect code.

effect-ts — Skill by teeverc

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/teeverc/effect-ts/effect-ts

Any agent

npx skills add teeverc/effect-ts --skill effect-ts

Clone the repo

git clone --depth 1 https://github.com/teeverc/effect-ts

Made for: Claude Code, Codex.

Per session 84 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.

When invoked 1,482 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.

Model	Per session	Once invoked
Fable 5	$0.00084	$0.01482
Opus 5	$0.00042	$0.00741
Sonnet 5	$0.00017	$0.00296
Haiku 4.5	$0.00008	$0.00148

Measured 2d ago against content hash 7c21720468a1, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

effect-ts 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 2d 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.

skills/effect-ts/SKILL.md · 105 lines

How it starts

The opening of the file, as written. The whole thing — 105 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Effect-TS

Overview

Provide workflows, patterns, and best practices for building Effect-based TypeScript programs, with focused references for errors, dependencies, resources, runtime execution, generators, schema, testing, platform modules, sink/stream processing, and Effect AI.

Primary docs and API sources:

https://effect.website/llms.txt (LLM-oriented topic index)
https://effect.website/docs
https://effect.website/docs/platform
https://effect.website/docs/ai/introduction
https://effect.website/docs/additional-resources/api-reference
https://tim-smart.github.io/effect-io-ai/ (concise API list)

For internal lookups, the effect-docs MCP can be used to search and fetch API references: https://github.com/tim-smart/effect-mcp.

Progressive Disclosure

Start with references/docs-index.md for topic routing.
Read one primary guide for the task.
Read one adjacent guide only if needed (for cross-cutting concerns like testing, runtime, or observability).
Avoid loading unrelated references.

Quick Triage

If it needs core Effect data types or combinators, open references/core-usage.md.
If it needs broader data-type choices (DateTime, BigDecimal, HashSet, Redacted), open references/data-types-advanced.md.
If it needs equality/order/hash semantics, open references/behavior-traits.md.
If the task is about error modeling or typed failures, open references/error-management.md.
If it needs error tooling (sandboxing, Cause, error-channel transforms), open references/error-tooling.md.
If it involves services/dependencies, open references/dependency-management.md.
If it involves layer construction or test wiring, open references/layer-patterns.md.
If it involves resource lifecycles, open references/resource-management.md.
If it involves running effects or runtime choice, open references/runtime-execution.md.
If it involves fibers or concurrency primitives, open references/concurrency.md.
If it involves interruption, supervision, or fiber refs, open references/concurrency-advanced.md.
If it involves schedules or repetition, open references/scheduling.md.
If it involves retries/backoff or schedule composition, open references/scheduling-retry.md.
If it involves streams, queues, pubsub, or STM, open references/streams-queues-stm.md.
If it involves HTTP clients or external APIs, open references/http-client.md.
If it involves HTTP servers or API definitions, open references/http-server.md.
If it involves request batching or data loaders, open references/request-resolver.md.
If it involves caching or memoization, open references/caching.md.
If it involves configuration or config providers, open references/configuration.md.
If it involves advanced config or redaction, open references/configuration-advanced.md.
If it involves logs, metrics, or tracing, open references/observability.md.
If it needs concrete logger/metrics/tracing setups or exporters, open references/observability-examples.md.
If it needs wiring of log/metric/trace layers, open references/observability-wiring.md.
If it needs sequential/branching readability, open references/generators.md.
If it needs runtime validation/decoding, open references/schema.md.
If it involves stream consumption patterns with reducers, open references/sink.md.
If it needs deterministic time in tests, open references/testing.md.
If it needs broader testing services, open references/testing-stack.md.
If it involves command/file/path/terminal/key-value modules, open references/platform-primitives.md.
If it involves LLM workflows, planning, or tool use via Effect AI, open references/ai.md.
If it involves bundle-size constrained runtimes, open references/micro.md.
If it involves migrating from Promise/async, open references/migration-async.md.
If it needs versioning or signature changes, open references/versioning.md.
If it hits common pitfalls or runtime errors, open references/troubleshooting.md.
If it needs result inspection or debugging, open references/exit-cause.md.
If it needs a docs-to-guide map from llms.txt, open references/docs-index.md.

Read the full file on GitHub · 105 lines

Files

What ships with it

37 files beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.

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.

2d ago First seen · 105 lines · 84 tokens per session scan A 7c21720468a1

Subscribe to this mod's changes

effect-ts is a skill published in the GitHub repository teeverc/effect-ts (5 stars, last pushed 2mo ago), licensed MIT. It adds 84 tokens to every session and 1,482 once invoked, about $0.0004 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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