`java.lang.NoClassDefFoundError` from javaagent built by `maven package`

Question

I've been trying to build javaagent (containing premain()) to .jar file using maven mvn package, and keep getting java.lang.NoClassDefFoundError exception related to external dependencies. For details, I added kafka-client dependecies and maven-jar-plugin to pom.xml like below

                <plugin>
                    <artifactId>maven-jar-plugin</artifactId>
                    <configuration>
                        <archive>
                            <index>true</index>
                            <manifest>
                                <addClasspath>true</addClasspath>
                                <classpathPrefix>lib</classpathPrefix>
                            </manifest>
                            <manifestEntries>
                                <mode>development</mode>
                                <url>${project.url}</url>
                                <key>value</key>
                                <Premain-Class>com.my.java.monitoring.Agent</Premain-Class>
                                <Can-Redefine-Classes>true</Can-Redefine-Classes>
                                <Can-Retransform-Classes>true</Can-Retransform-Classes>
                            </manifestEntries>
                        </archive>
                    </configuration>
                </plugin>

After reading How can I create an executable JAR with dependencies using Maven?, I tried using maven-assembly-plugin instead, like below

                <plugin>
                    <artifactId>maven-assembly-plugin</artifactId>
                    <configuration>
                        <descriptorRefs>
                            <descriptorRef>jar-with-dependencies</descriptorRef>
                        </descriptorRefs>
                        <archive>
                            <index>true</index>
                            <manifest>
                                <addClasspath>true</addClasspath>
                            </manifest>
                            <manifestEntries>
                                <Premain-Class>com.my.java.monitoring.Agent</Premain-Class>
                            </manifestEntries>
                        </archive>
                    </configuration>
                    <executions>
                        <execution>
                            <id>make-assembly</id>
                            <!-- this is used for inheritance merges -->
                            <phase>package</phase>
                            <!-- append to the packaging phase. -->
                            <goals>
                                <goal>single</goal>
                                <!-- goals == mojos -->
                            </goals>
                        </execution>
                    </executions>
                </plugin>

but I get this error => Failed to find Premain-Class manifest attribute in target/my-java-agent.jar Error occurred during initialization of VM agent library failed to init: instrument

Can anyone who has experience building javaagent .jar file with dependencies, please help.