When to Use Tooling API

Use Tooling API to perform the following tasks:

Manage working copies of Apex classes and triggers and Visualforce pages and components using the ApexClassMember, ApexTriggerMember, ApexPageMember, ApexComponentMember and MetadataContainer objects.
Manage working copies of static resource files using the StaticResource object.
Check for updates and errors in working copies of Apex classes and triggers and Visualforce pages and components, and commit changes to your organization using the ContainerAsyncRequest object.
Set heap dump markers using the ApexExecutionOverlayAction object.
Overlay Apex code or SOQL statements on an Apex execution using the ApexExecutionOverlayAction object.
Execute anonymous Apex. For sample code, see Using Tooling SOAP API and Using Tooling REST API.
Set checkpoints to generate log files for yourself or for other users using the TraceFlag object.
Access debug log and heap dump files using the ApexLog and ApexExecutionOverlayResult objects.
Manage custom fields on custom objects using the CustomField object.
Access code coverage results using the ApexCodeCoverage, ApexOrgWideCoverage and ApexCodeCoverageAggregate objects.
Execute tests, and manage test results using the ApexTestQueueItem and ApexTestResult objects.
Manage validation rules and workflow rules using the ValidationRule and WorkflowRule objects.

Selecting the Right API for Your Application

Tooling API provides both SOAP and REST interfaces.

Use REST API if you’re using a language that isn’t strongly typed, like JavaScript. See Using Tooling REST API.
Use SOAP API if you’re using a strongly typed language like Java that generates Web service client code. See Using Tooling SOAP API.