Determine the dataset that holds the information for which you are searching. Then decide what information you want from this dataset. The Census Bureau has already made available many datasets and is adding more almost monthly for querying with the API tool. Currently, the most popular aggregate datasets to query for variables using the API are as follows:
You can access a complete list of available datasets in the API Discovery Tool by going to <api.census.gov/data.html?key=your key here>. Be sure to replace the ‘your key here’ portion of the URL with your own API key.