The boolean type matches only two special values: true and false. Note that values that evaluate to true or false, such as 1 and 0, are not accepted by the schema.

In Python, "boolean" is analogous to bool. Note that in JSON, true and false are lower case, whereas in Python they are capitalized (True and False).
In Ruby, "boolean" is analogous to TrueClass and FalseClass. Note that in Ruby there is no Boolean class.
{ "type": "boolean" }

Values that evaluate to true or false are still not accepted by the schema: