Which tool is most likely used by an architect to diagnose issues with an inbound RESTful integration to Salesforce?

The most appropriate tool for diagnosing issues with an inbound RESTful integration to Salesforce is Workbench. Workbench is a powerful web-based suite of tools designed for developers and administrators to interact with Salesforce data in a flexible manner. It allows users to execute SOQL and SOSL queries, manipulate data, and perform various administrative tasks.

For diagnosing issues specifically related to RESTful integrations, Workbench offers features such as viewing logs, monitoring API calls, and analyzing requests and responses, which are essential for troubleshooting integration problems. The ability to send REST API requests and see the raw responses helps architects quickly identify where an integration may be failing, such as issues with authentication, incorrect endpoints, or data formatting problems.

While the other tools mentioned may serve particular functions within Salesforce, they are not tailored for diagnosing real-time issues with RESTful integrations. Data Loader is primarily used for bulk data manipulation, Force.com SOAP Explorer is specifically for SOAP-based integrations, and Metadata audit trail helps track changes in metadata rather than providing diagnostic capabilities for API integrations.

Thus, Workbench stands out as the best tool for conducting a thorough analysis of inbound RESTful integrations to identify and resolve issues effectively.