1. A server for validating input using a unified rule set, the server comprising: one or more processors configured to execute one or more modules of an application programming interface (API); and a memory storing the one or more modules of the API, the API comprising a definition of a unified rule set of input validation rules that are executable by different components of a system: wherein the unified rule set comprises two or more sets of input validation rules in which set membership is based in part on where an input validation rule is to be executed, the unified rule set comprising: a first set of input validation rules including rules that are to be executed by the API, and a second set of input validation rules including rules that are to be executed by a first component downward from the API, wherein the downward component is on a device separate from the server; wherein input is received from the downward component, wherein the input has been validated using the second set of validation rules; and whether the input is valid is determined using the first set of validation rules.