kotlin-sdk/samples/kotlin-mcp-client

Kotlin MCP Client

An interactive CLI client that connects to any MCP server over STDIO and pipes queries through Anthropic's Claude API.

Overview

This sample demonstrates a complete MCP client workflow: launching an MCP server as a subprocess, discovering its tools, converting them to Anthropic's tool format, and running an interactive chat loop where Claude can call server tools on behalf of the user.

Prerequisites

• JDK 17+
• An ANTHROPIC_API_KEY environment variable set with a valid Anthropic API key
• An MCP server script to connect to (.js, .py, or .jar)

Build & Run

Run the client, passing the path to an MCP server:

# Connect to a JVM server
./gradlew run --args="path/to/server.jar"

# Connect to a Python server
./gradlew run --args="path/to/server.py"

# Connect to a Node.js server
./gradlew run --args="path/to/build/index.js"

Note

The client uses STDIO transport, so it launches the MCP server as a subprocess. Ensure the server script is executable and is a valid .js, .py, or .jar file.

MCP Capabilities

From the client perspective, this sample demonstrates:

• Tool discovery — lists tools from the connected server and converts them to Anthropic's tool format.
• Tool invocation — when Claude's response requests a tool call, the client invokes the corresponding MCP tool and feeds the result back into the conversation.

Additional Resources

• MCP Specification
• Kotlin MCP SDK
• Anthropic Java SDK