Variable name/value pairs, one query parameter per Variable: Marital_Status=married sets the Variable Marital_Status to married. A Variable name starts with a letter or digit and holds only letters, digits, underscores (_), question marks (?), and dots (.). A dot only separates segments, as in Profile.Age: never first, never last, never two in a row, and the segment after it starts with a letter, digit, or underscore. A name never contains __ or ?., and never begins with fields. or include., which belong to those request parameters. As a regular expression: ^(?!.*__)(?!.*\?\.)(?!(?:fields|include)\.)[a-zA-Z0-9][a-zA-Z0-9_?]*(?:\.[a-zA-Z0-9_][a-zA-Z0-9_?]*)*$. The dot is part of the name, so Profile.Age, ProfileAge, and Profile_Age are three different Variables. Send a dotted name whole, as Profile.Age=42. Send a Date Variable as YYYY-MM-DD, such as DOB=1991-10-31, with no time or offset. A raw + reads as a space. See Dates.

JSONAPI-style sparse fieldsets. Use ?[field]=prop1,prop2 to limit returned fields or ?[field]= to return no data for that property. Omitting the fields querystring parameter entirely defaults to all properties being returned.

Trims the variables[] array. Omit it and the default applies: Variables with a null value, System Variables, and Constant Variables are all dropped — equivalent to the example below. Send all for every Variable, untrimmed. Each keyword also works on its own, and a modifier implies the base filter it modifies, so variables:!system drops null-valued Variables as well as System Variables. A value that is not a string or an array of strings returns HTTP 400.

Include additional data for debugging. stack adds the nodes the evaluation produced, before formatting. Do not use in Production.