mcp-stdio

MCP Stdio Server for Claude Desktop

This example demonstrates a standalone MCP server that communicates via stdio, allowing Claude Desktop to interact with your local system through MCP tools and resources.

Features

• Stdio Communication: Uses stdin/stdout for JSON-RPC 2.0 protocol
• Sandboxed File Access: Safe file operations within a designated directory
• Built-in Tools:
  • calculator: Basic math operations
  • read_file: Read files from sandbox
  • list_directory: List directory contents
• Resources: Sandbox information resource

Building

# Build the executable
go build -o hyperserve-mcp-stdio

# Or install globally
go install github.com/osauer/hyperserve/examples/mcp-stdio@latest

Claude Desktop Configuration

Add to your Claude Desktop configuration file:

macOS: ~/Library/Application Support/Claude/claude_desktop_config.json Windows: %APPDATA%\Claude\claude_desktop_config.json

{
  "mcpServers": {
    "hyperserve-local": {
      "command": "/path/to/hyperserve-mcp-stdio",
      "args": ["-sandbox", "/path/to/sandbox"]
    }
  }
}

Example Configuration

{
  "mcpServers": {
    "hyperserve-local": {
      "command": "/usr/local/bin/hyperserve-mcp-stdio",
      "args": ["-sandbox", "/Users/yourname/Documents/claude-sandbox", "-verbose"]
    }
  }
}

Command Line Options

• -sandbox <path>: Set sandbox directory (default: ~/.hyperserve-mcp/sandbox)
• -verbose: Enable verbose logging to stderr

Usage in Claude

Once configured, you can use the tools in Claude:

"Use the calculator tool to compute 15 * 24"
"List the files in the sandbox directory"
"Read the contents of hello.txt"

Security

• All file operations are restricted to the sandbox directory
• Path traversal attempts are blocked
• No network access or system commands

How It Works

This is a stdio server - it communicates via standard input/output:

• Reads JSON-RPC requests from stdin
• Writes JSON-RPC responses to stdout
• Logs to stderr (when using -verbose)

When you run it directly, it will appear to "hang" because it's waiting for input. This is normal!

Testing

Quick Test

# Single command test
echo '{"jsonrpc":"2.0","id":1,"method":"tools/list"}' | ./hyperserve-mcp-stdio | jq

# Run the included test script
./test.sh

Interactive Testing

# In one terminal, start the server with verbose logging
./hyperserve-mcp-stdio -verbose

# Type or paste JSON-RPC requests:
{"jsonrpc":"2.0","id":1,"method":"initialize","params":{"protocolVersion":"2025-11-25","capabilities":{},"clientInfo":{"name":"test","version":"1.0"}}}
{"jsonrpc":"2.0","id":2,"method":"tools/list"}
{"jsonrpc":"2.0","id":3,"method":"tools/call","params":{"name":"calculator","arguments":{"operation":"multiply","a":15,"b":4}}}

# Press Ctrl+D to exit

Troubleshooting

1. Check Claude Desktop logs: Look for MCP connection errors
2. Test manually: Run the server with -verbose flag
3. Verify path: Ensure the command path in config is correct
4. Permissions: Make sure the executable has execute permissions