Here is a list of all documented variables with links to the class documentation for each member:

- $ -

$ACCESS_TOKEN_SERVICE_HOOK : ApiHook
$accessTokenUrl : Platform
$actions : ServiceDefinition
$activityProgress : Outcome
$allowEmptyName : User
$allowJkuHeader : Jwt
$allowSharing : Tool
$approved : ResourceLinkShare
$authenticateUsingGet : Tool
$authenticationUrl : Platform
$authorizationServerId : Platform
$autoApprove : ResourceLinkShareKey
$base_string : OAuthRequest
$base_url_choice : ToolProfile
$baseUrl : Tool
$browserStorageFrame : Platform
$callback_url : OAuthConsumer
$capabilities : Message
$clientId : Platform
$code : AssessmentControlAction
$comment : Outcome
$constants : Message
$consumerGuid : Platform
$consumerName : Platform, ResourceLinkShare
$consumerVersion : Platform
$contentTypes : Tool
$context : ApiContext, Tool
$CONTEXT_ID_HOOK : ApiHook
$created : AccessToken, Context, ResourceLink, System, UserResult
$cssPath : Platform
$data_store : OAuthServer
$dataConnector : System
$dataSource : Outcome
$date : Outcome
$dateFormat : DataConnector
$db : DataConnector
$dbTableNamePrefix : DataConnector
$debugMode : System
$defaultEmail : Platform, Tool
$defaultLimit : Groups, LineItem, Membership, Result
$defaultTool : Tool
$deploymentId : Platform
$description : ResourceHandler, Item
$details : System
$disableFetchedPublicKeysSave : Util
$documentTarget : Placement
$documentTargets : Tool
$email : User
$enabled : System
$enabled_capability : Message
$enableFrom : System
$enableUntil : System
$encryptionMethod : System
$endpoint : LineItem, ServiceDefinition, Service
$error : HttpMessage
$errorOutput : Tool
$expires : AccessToken, PlatformNonce, ResourceLinkShareKey
$extraTime : AssessmentControlAction
$extRequest : ResourceLink
$extRequestHeaders : ResourceLink
$extResponse : ResourceLink
$extResponseHeaders : ResourceLink
$fileTypes : Tool
$firstname : User
$formats : ServiceDefinition
$formSubmissionTimeout : Util
$fullname : User
$gradingProgress : Outcome
$groups : Context, ResourceLink, User
$GROUPS_SERVICE_HOOK : ApiHook
$groupSets : Context, ResourceLink
$http_method : OAuthRequest
$http_url : OAuthRequest
$httpVersion : CurlClient
$icon : ResourceHandler
$icon_info : ResourceHandler
$id : Item, ServiceDefinition
$idScope : System
$image : User
$initiateLoginUrl : Tool
$item : ResourceHandler
$jku : System
$jwt : System
$key : OAuthConsumer, OAuthToken
$kid : System
$label : LineItem
$language : Outcome
$lastAccess : System
$lastname : User
$lastServiceRequest : Context, Platform, ResourceLink
$leeway : Jwt
$length : ResourceLinkShareKey
$life : Jwt, ResourceLinkShareKey
$logLevel : Util
$lti_version : ToolProfile, ToolProxy
$ltiContextId : Context
$ltiResourceLinkId : LineItem, ResourceLink
$ltiResultSourcedId : UserResult
$ltiUserId : Outcome, User
$ltiVersion : System
$maximumLength : PlatformNonce
$mediaType : Service
$mediaTypes : Tool
$MEMBERSHIPS_SERVICE_HOOK : ApiHook
$message : AssessmentControlAction, ResourceHandler, Tool
$message_type : Message
$MESSAGE_TYPES : Platform, Tool
$messageParameters : System
$messageUrl : Tool
$METHOD_NAMES : Util
$middlename : User
$name : Item, System
$ok : HttpMessage, System
$optionalMessages : ResourceHandler
$optionalServices : Tool
$OUTCOMES_SERVICE_HOOK : ApiHook
$output : Tool
$parameter : Message
$parameters : OAuthRequest
$path : Message
$platform : ApiPlatform, Tool
$platformId : Platform
$pointsPossible : LineItem
$POST_INPUT : OAuthRequest
$postMessageTimeoutDelay : Tool
$primaryResourceLinkId : ResourceLink
$product : Tool
$product_instance : ToolProfile
$profile : Platform
$protected : Platform
$rawParameters : System
$reason : System
$redirectionUris : Tool
$redirectUrl : Tool
$relativeLinks : HttpMessage
$request : HttpMessage
$requestHeaders : HttpMessage
$requestParameters : Util
$requiredMessages : ResourceHandler
$requiredScopes : System
$requiredServices : Tool
$resource_handler : ToolProfile
$resource_name : ResourceHandler
$resource_type : ResourceHandler
$resourceHandlers : Tool
$resourceId : LineItem
$resourceLink : ApiResourceLink, Tool
$resourceLinkId : ResourceLinkShare, ResourceLinkShareKey
$response : HttpMessage
$responseHeaders : HttpMessage
$responseJson : HttpMessage
$returnUrl : Tool
$roles : User
$rsaKey : System
$SCOPE : AssessmentControl, Groups, LineItem, Membership, Result, Score, ToolSettings
$scope : Service
$SCOPE_READONLY : LineItem
$scopes : AccessToken
$secret : OAuthConsumer, OAuthToken, System
$security_contract : ToolProxy
$shareApproved : ResourceLink
$shared_secret : SecurityContract
$signature_methods : OAuthServer
$signatureMethod : System
$sourcedId : User
$stateLife : Tool
$status : HttpMessage, Outcome
$strictMode : Util
$submissionCompleted : Outcome
$submissionReview : LineItem
$submissionStarted : Outcome
$submitFrom : LineItem
$submitUntil : LineItem
$tag : LineItem
$timeFormat : DataConnector
$timestamp : Item
$timestamp_threshold : OAuthServer
$title : Context, ResourceLink, ResourceLinkShare
$token : AccessToken
$tool : ApiTool
$tool_consumer_profile : ToolProxy
$tool_profile : ToolProxy
$tool_service : SecurityContract
$TOOL_SETTINGS_SERVICE_HOOK : ApiHook
$toolProxy : Platform
$type : Context, Outcome, Message
$unsigned : Service
$updated : AccessToken, Context, ResourceLink, System, UserResult
$url : Item
$USER_ID_HOOK : ApiHook
$username : User
$userResult : Tool
$variables : Message
$vendor : Tool
$version : OAuthRequest, OAuthServer, Item
$warnings : System