niklaserik/effect-mcp
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A Model Context Protocol (MCP) server dedicated to fetching the most current documentation from the Effect ecosystem.
@niklaserik/effect-mcp
A Model Context Protocol (MCP) server dedicated to fetching the most current documentation from the Effect ecosystem.
Purpose
This MCP server provides real-time access to Effect documentation for AI assistants and tools. It enables VS Code extensions and other MCP clients to retrieve accurate and up-to-date Effect package documentation to assist developers with questions about:
- The core
effect
package - Ecosystem packages (
@effect/platform
,@effect/ai
, etc.) - Both stable and unstable Effect packages
The server intelligently detects imported Effect packages in your code and fetches the most relevant documentation to answer your queries.
Features
- Real-time documentation access for Effect ecosystem
- Support for both stable and experimental packages
- Context-aware package detection based on imports
- Seamless integration with VS Code and other MCP-compatible clients
- Helps answer API usage questions for Effect developers
What this server exposes
- Resources (preferred)
- Dynamic template:
effect-docs://{libId}
- Completions on
{libId}
and resource listing are supported - Static aliases for discovery:
effect-docs://effect
,effect-docs://@effect-platform
, etc. - Supported libraries (as of now):
effect
@effect/platform
@effect/sql
@effect/vitest
@effect/ai
@effect/cli
@effect/cluster
@effect/rpc
@effect/typeclass
- Dynamic template:
- Tools (for compatibility)
effect-documentation
: fetch docs for selected libraries and return concatenated markdowneffect-doc-links
: return plain URIs to the resources above so clients can follow them
Caching & Retry
- In-memory TTL cache (~10 minutes) to avoid refetching unchanged docs.
- Lightweight retry with small backoff on transient fetch errors.
Installation
pnpm add @niklaserik/effect-mcp
Usage
For usage in VS Code or other MCP clients, refer to the client's documentation for adding custom MCP servers.
Quick test locally:
pnpm install
pnpm build
node dist/index.js # stdio transport
Then connect with an MCP client (e.g., MCP Inspector) over stdio and try:
- List resources and read
effect-docs://effect
- Call tool
effect-doc-links
with{ "libraries": ["effect", "@effect/platform"] }
Initialization instructions
- The server publishes short usage instructions via MCP initialize for clients that display them.
Development
# Install dependencies
pnpm install
# Build the project
pnpm build
# Run in development mode with auto-reload
pnpm dev
Notes:
- Built with
@modelcontextprotocol/sdk@^1.17.4
using the modernregisterResource
/registerTool
APIs. - Transport: stdio by default; can be adapted to Streamable HTTP if needed.
License
MIT