Burp or Burp Suite is a set of tools used for penetration testing of web applications. It is developed by a company named Portswigger who make freely available a Web Security Academy which has a range of lessons on penetration testing.

Requestly is an open-source tool that simplifies API development, testing, mocking, and integration for developers and QAs.

Automate API workflows. Chain HTTP requests. Validate. Zero code.

Meticulous monitors your daily interactions with your application as you develop it

LangSmith Observability gives you complete visibility into agent behavior with tracing, real-time monitoring, alerting, and high-level insights into usage.

Uptime Kuma is an easy-to-use self-hosted monitoring tool.