MCP Tools Usage From LangChain / Example in TypeScript

This simple Model Context Protocol (MCP) client demonstrates the use of MCP server tools by LangChain ReAct Agent.

It leverages a utility function convertMcpToLangchainTools() from @h1deya/langchain-mcp-tools.
This function handles parallel initialization of specified multiple MCP servers and converts their available tools into an array of LangChain-compatible tools (StructuredTool[]). It also performs LLM provider-specific schema transformations to prevent schema compatibility issues

OpenAI's gpt-5.4-mini is used as the LLM. For convenience, code for OpenAI's and Anthropic's LLMs are also included and commented out.

A bit more realistic (conversational) MCP Client is available here

A python equivalent of this app is available here

Prerequisites

• Node.js 18+
• npm 8+ (npx) to run Node.js-based MCP servers
• [optional] npm 7+ (npx) to run Node.js package-based local MCP servers
• [optional] uv (uvx) installed to run Python-based MCP servers
• LLM API keys from OpenAI, Anthropic, Google GenAI, and/or xAI as needed

Usage

1. Install dependencies:

   npm install
   

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2. Setup API key:

   cp .env.template .env
   

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   • Update .env as needed.
   • .gitignore is configured to ignore .env to prevent accidental commits of the credentials.

3. Run the app:

   npm start
   

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License

MIT