First, you probably should not post your api key in a public forum.

Second, from the doc for HTTP::Tiny:

headers — A hashref containing headers to include with the request. If the value for a header is an array reference, the header will be output multiple times with each value in the array. These headers over-write any default headers.

Third,

use Types::Serializer;

$json = encode_json [Types::Serialiser::true];
[download]

should sort your boolean error.

Hope this helps!