strace - Trace system calls and signals. A diagnostic, debugging and instructional userspace utility.
Postman - The Collaboration Platform for API Development
ftrace - A function tracer for the Linux kernel.
Insomnia REST - The most intuitive cross-platform REST API Client ð´
Valgrind - Valgrind is an instrumentation framework for building dynamic analysis tools.
Hoppscotch - Open source API development ecosystem