Using Amazing Fields API
Amazing Fields for Trello provides a REST API for accessing all your Trello card data including fields.
Amazing Fields provides an API for supporters to read their fields remotely. All data for Amazing Fields is stored on the Trello servers, but it is compressed and encoded to allow users to store more data. The API provides a simple wrapper that makes the calls to Trello on your behalf and then decodes the data into an easy to use format.
Please see the Trello API documentation for full details on all the data provided by Trello. The majority of the data returned by the Amazing Fields API is standard Trello data with the same structure and meaning as described in the Trello API documentation.
Allocate API Token
API access is controlled using a token that is tied to your specific Trello user account. To allocate a token, open the Amazing Fields Settings panel, then go to the "Board Settings" tab. Look for the section about API Access and read the instructions there.
Once you have your API token, you can make requests to the Amazing Fields API using the token.
See the data returned from the API for the most up-to-date version of the data schema. Note that the data schema embedded Amazing Fields data within the data normally returned from the Trello board REST endpoint.
The Amazing Fields configuration data that is returned is not guaranteed to be 100% stable across versions. I tend to keep it stable, but it could change in the future. One of the reasons for this is that the data format is partially minified to save space in how it is stored in Trello. Where useful I have expanded some identifier fields with an additional field postfixed with _str. This is meant to provide a more user readable value.
If you see other places where I could expand the API to support your usecase, please contact me through support and let me know how I can make it more useful for you.