REpresentational State Transfer (REST) Application Programming Interfaces (APIs) are widely used for the communication between loosely coupled web services. While the loose coupling allows services to evolve independently, it requires development teams to actively identify changes in their REST APIs to notify teams of affected services. If overlooked, changes can result in unexpected breaking changes that lead to failures in the affected service. In this paper, we present AutoGuard, our tool for automatically extracting and reporting breaking changes of REST APIs in services developed with the popular Java Spring Boot framework. AutoGuard consists of two components: the first component generates the OpenAPI descriptions of two versions of a REST API from the source code; the second component extracts and logs the differences between them and reports the API breaking changes. AutoGuard’s static analysis does not require running a service to understand its REST API changes, enabling direct integration into the development process. We integrated AutoGuard into GitHub’s and GitLab’s continuous integration workflows, where it automatically generates the REST API change logs for pull and merge requests and reports any breaking changes. With this information, developers and code reviewers can make informed decisions on how to proceed with the requests. Video demonstration: https://youtu.be/3qeWIVfMvWE Tool repository: https://github.com/MSA-API-Management/AutoGuard