Service Annotations

Service/RPC Annotations

Annotations use the google closure compiler syntax to

  • describe the service

  • validate RPC inputs

    • cast to correct type

    • uniform error reporting for invalid inputs (to the end user)

  • populate the help messages for the end user

  • make your code more readable and maintainable

Service Annotations

An annotation tagged with @service will be used to describe the Service and is shown to the user when getting help about the call <service> <RPC> block without any RPC set. An example is provided below:

* The IEXTrading Service provides access to real-time and historical stock price data.
* For more information, check out
* Terms of use:
* @service

RPC Annotations

RPC annotations can be used for RPC input validation and generating help messages for the user. An example of an annotation block for the city RPC from the geolocation service is shown below.

* Get the name of the city nearest to the given latitude and longitude.
* @param {Latitude} latitude latitude of the target location
* @param {Longitude} longitude longitude of the target location
* @returns {String} city name
*/ = function (latitude, longitude) {

Annotation blocks should be close to the RPC/function definition.

Read more: Annotations Guide

Essential Tags

  • required param: @param {Type} name description sentence...

  • optional param: @param {Type=} name description sentence...

  • required object field: @param {Type} objectName.fieldName description sentence...

  • optional object field: @param {Type=} objectName.fieldName description sentence...

  • return value: @returns {Type} description sentence...

  • no return value: no annotation needed

Supported Types

When both JavaScript and NetsBlox types exist, the types are specified using the JavaScript type. For example, Array is used instead of List. Here are some of the common parsers that are available (note that values inside angled brackets <...> are optional; if one is omitted, in general that constraint is not enforced):

  • Number

  • BoudedNumber<min, max> - This limits the range of a Number. For example, BoundedNumber<0> guarantees a non-negative number.

  • Latitude

  • Longitude

  • String

  • BoundedString<min, max> - This is used to put limits on the length of a String input.

  • Array<Type, min, max>

  • Boolean

  • Enum<option1,option2,option3,...> - This is essentially a String value, except that you are guaranteed it will be one of the listed options.

  • Date

  • Object - This is only used for defining structured data (list of key-value pairs). See Essential Tags for how to define fields. Currently, if no fields are specified, any field name is allowed to be passed by the user.

For a full list of the standard parsers, or more information on how to make a custom parser, see the source code.