LangSearch MCP Server
A Model Context Protocol (MCP) server that provides access to LangSearch's Web Search API and Semantic Rerank API. This server enables AI assistants to perform web searches and rerank search results based on semantic relevance.
Features
- Web Search: Search the web with advanced filtering options (freshness, result count, summaries)
- Semantic Rerank: Rerank documents based on semantic relevance to a query
Tools
1. langsearch_web_search
Search the web using LangSearch's Web Search API.
Parameters:
query(string, required): The search queryfreshness(string, optional): Filter results by freshness - "noLimit" (default), "onLimit", "day", "week", "month"summary(boolean, optional): Include full summaries in results (default: true)count(number, optional): Number of results to return (1-50, default: 10)
Returns:
- Structured search results with titles, URLs, snippets, and optional summaries
- Query context and metadata
2. langsearch_semantic_rerank
Rerank documents based on semantic relevance to a query.
Parameters:
query(string, required): The search query to compare against documentsdocuments(array of strings, required): List of document texts to reranktop_n(number, optional): Number of top results to return (default: all documents)return_documents(boolean, optional): Whether to include document text in response (default: true)
Returns:
- Reranked documents with relevance scores (0-1 scale)
- Original document indices and optional text content
Installation
- Clone or download this repository
- Install dependencies:
npm install
- Build the project:
npm run build
- Copy
.env.exampleto.envand add your LangSearch API key:
cp .env.example .env
- Edit
.envand set your API key:
LANGSEARCH_API_KEY=your-api-key-here
Getting a LangSearch API Key
Visit LangSearch to sign up and obtain an API key.
Usage
With Claude Desktop
Add the server to your Claude Desktop configuration file:
macOS: ~/Library/Application Support/Claude/claude_desktop_config.json
Windows: %APPDATA%\Claude\claude_desktop_config.json
{
"mcpServers": {
"langsearch": {
"command": "node",
"args": [
"/absolute/path/to/langsearch-mcp-ts/dist/index.js"
],
"env": {
"LANGSEARCH_API_KEY": "your-api-key-here"
}
}
}
}
Replace /absolute/path/to/langsearch-mcp-ts with the actual path to this project directory.
After configuration, restart Claude Desktop. The LangSearch tools will be available in your conversations.
Standalone Mode
Standalone Mode
Development Mode
Run the server in development mode with auto-reload:
npm run dev
Production Mode
Build and run the compiled server:
npm run build
npm start
Testing with MCP Inspector
Test the server using the MCP Inspector:
npm run inspector
Then select "stdio" transport and provide the path to the server executable.
Configuration
The server uses environment variables for configuration:
LANGSEARCH_API_KEY(required): Your LangSearch API keyLANGSEARCH_BASE_URL(optional): Custom API base URL (default: https://api.langsearch.com)
Example Usage
Web Search Example
{
"name": "langsearch_web_search",
"arguments": {
"query": "latest developments in AI",
"freshness": "week",
"summary": true,
"count": 5
}
}
Semantic Rerank Example
{
"name": "langsearch_semantic_rerank",
"arguments": {
"query": "climate change solutions",
"documents": [
"Renewable energy is the future of power generation.",
"The stock market reached new highs today.",
"Carbon capture technology shows promise in reducing emissions."
],
"top_n": 2,
"return_documents": true
}
}
API References
Error Handling
The server implements comprehensive error handling:
- Invalid API keys return clear error messages
- Network errors are caught and reported
- Input validation ensures correct parameter types and ranges
- All errors are returned with
isError: trueflag
TypeScript
This server is written in TypeScript with full type safety. All API responses and tool parameters are properly typed using zod schemas for runtime validation.
License
MIT