I've read through the documentation on decoding a transaction via API on Blockr:

http://blockr.io/documentation/api

I have the hex code, which correctly decodes on http://blockr.io/tx/push

Thus it can decode.

Please show me where I am going wrong trying to follow the API documentation which states:

My attempt includes adding the path to postman (as a post):

http://btc.blockr.io/api/v1/tx/decode?hex=010000000117f244eba4...