1. A computer system comprising: a processor for executing instructions stored in a computer-readable medium on one or more devices providing an application development tool; wherein the application development tool comprises one or more modules configured to perform operations comprising: receiving an input modifying source code of an application, the source code providing one or more elements of the application when executed at runtime; determining that the input specifies a reference in the source code to data returned by an interaction with a data source at runtime; and responsive to determining that the input specifies the reference to the data returned by the interaction with the data source: querying the data source and receiving a returned data sample comprising one or more data parameters in response to the query, wherein the one or more data parameters are communicated between the application and the data source at runtime to access data associated with the one or more data parameters; characterizing the returned data sample, wherein characterizing the returned data sample comprises determining, from the returned data sample, a data structure definition for the returned data sample and a source code element for referring to the one or more data parameters; and providing output comprising a suggested type characterization for the data returned by the interaction, wherein the suggested type characterization comprises at least one of (i) one or more options for completing an incomplete reference in the source code to the one or more data parameters and (ii) a suggested syntax of a source code segment referencing the one or more data parameters.