Looking for a chaotic test library to test REST API

I want to test my REST API (JSON-based) with a tool that takes a typical JSON input, and adds chaos to it. For example, say we have an API that accepts this JSON:

{
  "name" : "Bob",
  "address" : "123, Sunny St"
}

The tool would do this:

{
  "name" : true,
  "address" : "123, Sunny St"
}

Then:

{
  "name" : true,
  "address" : 156
}

Then:

{
  "name" : true,
  "address" : 156,
  "foo0" : "bar"
}

and so on and so forth, and start again from scratch and take it another direction.

Each request is exactly one change.

I could swear I have heard of such a tool before. Please help me if you know one.