https://curl.se/ has been account free since 1998.

Never understood why people keep trying to use proprietary tools for this, especially when curl is so good.

I have a directory of shell scripts I use to test out endpoints. I persist request/response data either with environment variables or regular files. Oh and since these are just shell scripts, it's pretty trivial to do stuff like iterate over a CSV (or JSON array) and make a request for each row, conditionally make requests, or whatever else you want.

Oh and honorable mention goes to jo and jq for making it super easy to make/process JSON data.