Context7 MCP Server (37.1k stars)

Up-to-date documentation for 8,500+ libraries. Prevents hallucinated APIs by providing current, version-specific docs.

When to Use

• Effect-TS: APIs change frequently, training data outdated
• Any library where unsure of current API
• Before writing code with external imports
• When user asks "how do I use X?"
• Verifying function signatures and parameters

Trigger Phrase

use context7 - how do I create an Effect Layer?

Tools

resolve-library-id

Find Context7-compatible library ID from package name.

mcp__context7__resolve-library-id({
  libraryName: "effect"
})

Returns:

• Library ID (format: /org/project)
• Description
• Code snippet count
• Source reputation (High/Medium)
• Benchmark score (0-100)

get-library-docs

Fetch documentation for a library.

mcp__context7__get-library-docs({
  context7CompatibleLibraryID: "/effect-ts/effect",
  topic: "Layer",
  mode: "code",    // "code" for API/examples, "info" for concepts
  page: 1          // Pagination 1-10
})

Common Library IDs

Usage Patterns

Before Implementing New Feature

1. resolve-library-id to get correct ID
2. get-library-docs with relevant topic
3. Use mode="code" for implementation examples

Understanding Concepts

1. get-library-docs with mode="info"
2. Paginate (page=2, page=3) for comprehensive coverage

Effect-TS (Critical)

The Effect API changes frequently. Training data is outdated.

Always query context7 before writing Effect code:

mcp__context7__get-library-docs({
  context7CompatibleLibraryID: "/effect-ts/effect",
  topic: "Effect.gen"
})

Mode Selection