title: What exactly is "tools.jar" in the Android SDK?
body: <p>So, I've been trying to build a project in LibGDX for about 10 hours now. In case you'r unfamiliar, LibGDX is one of those platforms where you specify a project directory at the start, along with any required SDKs and then when you're ready to start coding it will generate a project for you.</p>
  
  <p>Anyway, I've been having a problem where every time I try to build it fails with the single error message:</p>
  
  <blockquote>
    <p>Execution failed for task :core:compileJava.</p>
    
    <blockquote>
      <p>Could not find tools.jar</p>
    </blockquote>
  </blockquote>
  
  <p>I'm guessing "tools.jar" is a package within the Android SDK, as this is the only repository needed to build, it doesn't ask for a JRE or even the Java SDK. just the Android SDK. </p>
  
  <p>I have been looking in the SDK manager, I have installed all of the packages labelled "Android-SDK Tools", "Android-SDK Platform Tools" and "Android SDK Build Tools" but there is nothing else that includes "tools.jar", I am looking for some light shed on this topic as it is a very grey area. I would like to know where this .jar file comes from and what exactly it includes. Can it be installed from the Android SDK?</p>
  
  <p>There have been similar questions like this before which only fit narrow situations, If someone could provide a holistic description of the tools.jar package it would benefit a great deal for me and everyone else that needs it in their 3rd-party android IDEs.</p>
  
  <p>For the record, it's building with Gradle and my current SDK is well-equipped enough to build full-fledged apps in Android Studio.</p>
  
  <p><strong>Please don't answer this question with a question</strong> unless I have left out some information that is dire to finding an adequate solution </p>