feat: Add Serpex web search tool integration

[divyeshradadiya]

feat(serpex): Add Serpex web search tool integration

Description

This PR adds official Serpex web search integration to LangChain.js. Serpex provides multi-engine web search results in structured JSON format, supporting Google, Bing, DuckDuckGo, Brave, Yahoo, and Yandex search engines with intelligent auto-routing and retry logic.

Changes

• Add Serpex tool for multi-engine web search (Google, Bing, DuckDuckGo, Brave, Yahoo, Yandex)
• Support for auto-routing with retry logic
• Configurable search parameters (engine, category, time_range)
• Comprehensive test suite
• Full documentation with examples
• API endpoint: https://api.serpex.dev

Files Added

• libs/langchain-community/src/tools/serpex.ts - Main Serpex tool implementation
• libs/langchain-community/src/tools/tests/serpex.test.ts - Comprehensive test suite
• SERPEX_INTEGRATION.md - Integration documentation with examples

Files Modified

• libs/langchain-community/src/load/import_map.ts - Added Serpex import mapping

Features

• 🔍 Multi-Engine Support: Automatic routing across 7 search engines (auto, google, bing, duckduckgo, brave, yahoo, yandex)
• ⚙️ Configurable Parameters: engine, category (web), time_range (all, day, week, month, year)
• 🛡️ Error Handling: Robust error handling with detailed error messages
• 📦 Response Parsing: Intelligent parsing for answers, results, suggestions, corrections
• 🔄 Agent Compatible: Works seamlessly with LangChain agents and chains

API Details

• Endpoint: https://api.serpex.dev/api/search
• Authentication: Bearer token in Authorization header
• Cost: 1 credit per request (all engines)
• Rate Limit: 300 requests/second

Testing

All tests pass successfully with real API:

• ✅ Basic Search (auto engine) - 11 results, 1200ms
• ✅ Google Search with Time Range - 14 results, 1400ms
• ✅ Bing Search - 18 results, 1734ms
• ✅ DuckDuckGo Search - 7 results, 837ms

Run tests:

npm test libs/langchain-community/src/tools/tests/serpex.test.ts

Or with real API:

SERPEX_API_KEY=your-key node test_langchain_js_integration.js

Backwards Compatibility

✅ No breaking changes. This is a new tool addition that doesn't affect existing functionality.

Dependencies

No new dependencies required. Uses existing LangChain dependencies and native fetch API.

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Thanks for reviewing! This integration provides seamless multi-engine web search for LangChain.js applications.

My Twitter - @kartey_r

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