using blockchain.info api_code I make a JSON call to

https://blockchain.info/tobtc?currency=USD&amp;value=1

This is a free api with a request limit.

I have just received my api_code via email. This is blockchain.info's example of how to use it


  Once approved the API Code can be passed to all requests in the "api_code" parameter e.g. https://blockchain.info?api_code=$your_code


I am guessing that they mean with PHP (because of the dollar sign) as when I type into my address bar

https://blockchain.info/tobtc?api_code=000my0-api00-code-0000-000000000&amp;currency=USD&amp;value=1


The data does not any look different when I use the api code with the dollar

https://blockchain.info/tobtc?api_code=$000my0-api00-code-0000-000000000&amp;currency=USD&amp;value=1


Though I am unsure of how to tell what is the correct way as I can access this free api with and without an api code (with a request limit). How do I tell if I am adding it correctly?
The first one is correct.
https://blockchain.info/tobtc?api_code=000my0-api00-code-0000-000000000&amp;currency=USD&amp;value=1

However, the particular call you are using (/tobtc) is public and thus needs no api_code attached.

https://blockchain.info/tobtc?currency=USD&amp;value=1