Effect Library Lookup

Quick reference for finding and understanding Effect TypeScript library APIs from local source code.

Source Code Access

Source code is available locally and on GitHub. Check local first, fall back to GitHub if not available.

Repo	Local path	GitHub
Effect	`opensrc/repos/github.com/effect-ts/effect/`	https://github.com/effect-ts/effect
EffectPatterns	`opensrc/repos/github.com/PaulJPhilp/EffectPatterns/`	https://github.com/PaulJPhilp/EffectPatterns

When to Use This Skill

Use this skill when:

•Looking up Effect function signatures or implementations
•Finding examples of Effect patterns (Effect.gen, Layer, Context, etc.)
•Understanding how Effect modules work internally
•Checking API availability or deprecation status
•Learning Effect idioms from source code

How to Look Up Effect APIs

1. Use the Effect Docs MCP Server (Fastest)

The effect-docs MCP server provides indexed documentation:

code

mcp__effect-docs__effect_docs_search: Search for Effect concepts
mcp__effect-docs__get_effect_doc: Get specific documentation by ID

2. Search the Local Source

For implementation details, search the local source at opensrc/repos/github.com/effect-ts/effect/:

bash

# Find a specific function
grep -r "export const myFunction" opensrc/repos/github.com/effect-ts/effect/packages/effect/src/

# Find usage patterns
grep -rn "Effect.gen" opensrc/repos/github.com/effect-ts/effect/packages/effect/src/

# Find type definitions
grep -rn "interface MyType" opensrc/repos/github.com/effect-ts/effect/packages/effect/src/

3. Read Source Files Directly

Core modules are at: opensrc/repos/github.com/effect-ts/effect/packages/effect/src/<Module>.ts

Example: To understand Effect.map, read opensrc/repos/github.com/effect-ts/effect/packages/effect/src/Effect.ts

Quick Reference

Task	Reference
Module categories	`references/modules.md`
Common patterns	`references/patterns.md`

Package Structure

text

opensrc/repos/github.com/effect-ts/effect/
├── packages/
│   ├── effect/               # Core Effect library
│   │   └── src/              # Source files (Effect.ts, Layer.ts, etc.)
│   ├── platform/             # Cross-platform utilities (HTTP, FileSystem)
│   ├── platform-node/        # Node.js platform implementation
│   ├── platform-browser/     # Browser platform implementation
│   ├── cli/                  # CLI building utilities
│   ├── sql/                  # SQL database utilities
│   ├── sql-pg/               # PostgreSQL implementation
│   ├── sql-kysely/           # Kysely integration
│   ├── rpc/                  # Remote procedure calls
│   ├── cluster/              # Distributed computing
│   ├── opentelemetry/        # OpenTelemetry integration
│   ├── experimental/         # Experimental features
│   └── ai/                   # AI integrations (OpenAI, Anthropic, etc.)

Core Modules Quick Lookup

Effect System

Module	File	Purpose
Effect	`Effect.ts`	Core effect type and combinators
Layer	`Layer.ts`	Dependency injection layers
Context	`Context.ts`	Type-safe service context
Scope	`Scope.ts`	Resource management
Runtime	`Runtime.ts`	Effect execution

Data Types

Module	File	Purpose
Option	`Option.ts`	Optional values
Either	`Either.ts`	Success/failure values
Chunk	`Chunk.ts`	Immutable arrays
HashMap	`HashMap.ts`	Immutable hash maps
HashSet	`HashSet.ts`	Immutable hash sets
List	`List.ts`	Immutable linked lists

Concurrency

Module	File	Purpose
Fiber	`Fiber.ts`	Lightweight threads
Queue	`Queue.ts`	Concurrent queues
Ref	`Ref.ts`	Mutable references
Semaphore	`Semaphore.ts`	Concurrency limiting
PubSub	`PubSub.ts`	Publish/subscribe

Schema & Validation

Module	File	Purpose
Schema	`Schema.ts`	Data validation & encoding
ParseResult	`ParseResult.ts`	Parsing results
Arbitrary	`Arbitrary.ts`	Property-based testing

Streaming

Module	File	Purpose
Stream	`Stream.ts`	Effectful streams
Sink	`Sink.ts`	Stream consumers
Channel	`Channel.ts`	Bidirectional streaming

Scheduling & Time

Module	File	Purpose
Schedule	`Schedule.ts`	Retry/repeat schedules
Duration	`Duration.ts`	Time durations
DateTime	`DateTime.ts`	Date/time handling
Clock	`Clock.ts`	Time service
Cron	`Cron.ts`	Cron expressions

Configuration

Module	File	Purpose
Config	`Config.ts`	Type-safe configuration
ConfigProvider	`ConfigProvider.ts`	Configuration sources

Common Lookup Patterns

Find Function Signature

bash

# In Effect.ts, functions are well-documented with JSDoc
grep -A 20 "export const map" opensrc/repos/github.com/effect-ts/effect/packages/effect/src/Effect.ts

Find Type Definition

bash

# Look for interface or type alias
grep -n "interface Effect<" opensrc/repos/github.com/effect-ts/effect/packages/effect/src/Effect.ts

Find Examples in Tests

bash

# Tests often have practical examples
grep -rn "Effect.gen" opensrc/repos/github.com/effect-ts/effect/packages/effect/test/

Check Platform APIs

bash

# HTTP client/server
ls opensrc/repos/github.com/effect-ts/effect/packages/platform/src/Http*.ts

# FileSystem
cat opensrc/repos/github.com/effect-ts/effect/packages/platform/src/FileSystem.ts

EffectPatterns Knowledge Base

Community-driven patterns and architectural guides at opensrc/repos/github.com/PaulJPhilp/EffectPatterns/.

bash

# Browse pattern categories
ls opensrc/repos/github.com/PaulJPhilp/EffectPatterns/content/

# Search for a specific pattern
grep -rn "Layer" opensrc/repos/github.com/PaulJPhilp/EffectPatterns/content/

# Read docs
ls opensrc/repos/github.com/PaulJPhilp/EffectPatterns/docs/

Covers: getting started, core concepts, error management, resource management, concurrency, streams, scheduling, domain modeling, schema, platform, HTTP APIs, data pipelines, testing, and observability.

External References

•Effect Website - Official documentation
•Effect API Reference - Full API docs
•Effect Discord - Community support

Tips for Effective Lookups

•Start with MCP search - Use effect_docs_search for conceptual questions
•Read JSDoc comments - Effect source has excellent inline documentation
•Check tests for examples - Test files show real usage patterns
•Use module tables above - Quickly navigate to the right source file
•Platform packages - HTTP, FileSystem, etc. are in @effect/platform
•EffectPatterns - Use for architectural patterns and best practices