A lightweight CLI-based Model Context Protocol (MCP) client designed for testing and debugging MCP servers. This tool allows developers to interact with any MCP-compliant server directly from their terminal without needing to set up a full LLM environment like Cursor or Claude Desktop.
This project was born out of a practical need. While testing MCP servers in IDEs like Cursor is convenient, users often face free usage limits which can halt development. To avoid these restrictions and provide a way for developers without premium subscriptions to test their servers freely and infinitely, I built this standalone client.
- MCP Server Developers: Quickly verify if your tools are correctly exposed and responding as expected.
- LLM Integrators: Understand the JSON-RPC interface of the Model Context Protocol.
- System Architects: Test tool-calling logic and data structures in isolation.
- List Tools: Retrieve all tools exposed by your MCP server.
- Call Tools: Execute specific tools with custom JSON arguments.
- Lightweight: Minimal dependencies (
node-fetchandreadline). - Interactive CLI: Simple command-based interface.
- Node.js (v16 or higher recommended)
- A running MCP server (default expected at
http://localhost:8080/mcp)
- Clone the repository or download the files.
- Install dependencies:
npm install
Run the client:
node mcp-client.jsOnce started, you can use the following commands:
| Command | Description | Example |
|---|---|---|
tools |
Lists all available tools from the server | tools |
call |
Calls a tool with JSON arguments | call my_tool {"arg1": "value"} |
While this client is built using Node.js, its utility is universal:
- Server Agnostic: It can communicate with any MCP server, whether the server is written in Python, Go, Rust, Java, or Node.js.
- Protocol Based: As long as the server follows the Model Context Protocol and is accessible over HTTP, this client can interact with it.
- No More "Black Box" Testing: Avoid the complexity of testing servers inside AI apps where logs might be hidden.
- Bypass Usage Limits: Test your MCP server as much as you want without worrying about Cursor or Claude's daily message limits.
- Fast Iteration: Test tool changes instantly without restarting your primary IDE or LLM client.
- Protocol Verification: Ensure your server strictly adheres to the JSON-RPC 2.0 standards used by MCP.
By default, the client connects to http://localhost:8080/mcp. You can modify the BASE_URL at the top of mcp-client.js if your server is running on a different port or path.
const BASE_URL = "http://your-server-url:port/mcp";Built with ❤️ for the MCP Ecosystem.