Every plugin needs to have at least one class with the @PluginConfiguration annotation. This provides ReadyAPI with metadata about the plugin as a whole, and is required for the plugin to actually work.

package com.smartbear.ready.plugin.template;

import com.eviware.soapui.plugins.PluginAdapter;
import com.eviware.soapui.plugins.PluginConfiguration;

@PluginConfiguration(groupId = "com.smartbear.ready.plugins",
name = "ReadyAPI Plugin Template", version = "1.0",
autoDetect = true, description = "A Sample ReadyAPI Plugin",
infoUrl = "https://github.com/smartbear/ready-api-plugin-template")
public class PluginConfig extends PluginAdapter {
}