If you are testing REST , it happens that you need to prettify JSON. With Python you do not need any other tool except your terminal!

Example

{"glossary":{"title":"example glossary","GlossDiv":{"title":"S","GlossList":{"GlossEntry":{"ID":"SGML","SortAs":"SGML","GlossTerm":"Standard Generalized Markup Language","Acronym":"SGML","Abbrev":"ISO 8879:1986","GlossDef":{"para":"A meta-markup language, used to create markup languages such as DocBook.","GlossSeeAlso":["GML","XML"]},"GlossSee":"markup"}}}}}

Now open you terminal…

# Using module json.tool to prettify and validate
$ cat example.json | python -m json.tool
{
    "glossary": {
        "GlossDiv": {
            "GlossList": {
                "GlossEntry": {
                    "Abbrev": "ISO 8879:1986",
                    "Acronym": "SGML",
                    "GlossDef": {
                        "GlossSeeAlso": [
                            "GML",
                            "XML"
                        ],
                        "para": "A meta-markup language, used to create markup languages such as DocBook."
                    },
                    "GlossSee": "markup",
                    "GlossTerm": "Standard Generalized Markup Language",
                    "ID": "SGML",
                    "SortAs": "SGML"
                }
            },
            "title": "S"
        },
        "title": "example glossary"
    }
}