HTTPie
For those moments when you are asked to integrate a new API into an application and you want to take a look around before any code is written, then HTTPie is a great tool.
HTTPie can be used for testing, debugging, and generally interacting with HTTP servers.
I discovered it via SWAPI which uses HTTPie for examples in their documentation.
http swapi.co/api/planets/1/
{
"climate": "arid",
"created": "2014-12-09T13:50:49.641000Z",
"diameter": "10465",
"edited": "2014-12-21T20:48:04.175778Z",
"films": [
"http://swapi.co/api/films/5/",
"http://swapi.co/api/films/4/",
"http://swapi.co/api/films/6/",
"http://swapi.co/api/films/3/",
"http://swapi.co/api/films/1/"
],
"gravity": "1 standard",
"name": "Tatooine",
"orbital_period": "304",
"population": "200000",
"residents": [
"http://swapi.co/api/people/1/",
"http://swapi.co/api/people/2/",
"http://swapi.co/api/people/4/",
"http://swapi.co/api/people/6/",
"http://swapi.co/api/people/7/",
"http://swapi.co/api/people/8/",
"http://swapi.co/api/people/9/",
"http://swapi.co/api/people/11/",
"http://swapi.co/api/people/43/",
"http://swapi.co/api/people/62/"
],
"rotation_period": "23",
"surface_water": "1",
"terrain": "desert",
"url": "http://swapi.co/api/planets/1/"
}Couple it with jq, a command line JSON processor and you have all the tools you need for API investigation from the command line.
http swapi.co/api/planets/1/ | jq '.name'
"Tatooine"