I've created a simple control to see what the attribute 'usage' on a property does in the form editor UI.Whenever I included a usage=output I would ge

Hi Menik,This is actually a documentation defect , we accidently got it included. We have not exposed this functionality for public preview yet

Solved: Error during saving form when an control with an output parameter in included

I cannot attach .txt files so here's the content:

Unhandled exception: 
Exception type: System.ServiceModel.FaultException`1[Microsoft.Xrm.Sdk.OrganizationServiceFault]
Message: The type attribute is missing from the declaration of Property OutputDetail: 
<OrganizationServiceFault xmlns:i="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://schemas.microsoft.com/xrm/2011/Contracts">
 <ActivityId>ae3236d6-f4ae-4960-9e58-43739af29027</ActivityId>
 <ErrorCode>-2147220970</ErrorCode>
 <ErrorDetails xmlns:d2p1="http://schemas.datacontract.org/2004/07/System.Collections.Generic">
 <KeyValuePairOfstringanyType>
 <d2p1:key>ApiExceptionSourceKey</d2p1:key>
 <d2p1:value xmlns:d4p1="http://www.w3.org/2001/XMLSchema" i:type="d4p1:string">Plugin/Microsoft.Crm.ObjectModel.SystemFormService</d2p1:value>
 </KeyValuePairOfstringanyType>
 <KeyValuePairOfstringanyType>
 <d2p1:key>ApiOriginalExceptionKey</d2p1:key>
 <d2p1:value xmlns:d4p1="http://www.w3.org/2001/XMLSchema" i:type="d4p1:string">Microsoft.Crm.CrmException: The type attribute is missing from the declaration of Property Output ---&gt; Microsoft.Crm.CrmException: The type attribute is missing from the declaration of Property Output
 at Microsoft.Crm.ObjectModel.CustomControlParameterValidationHelper.MakeEntryForTypeAttribute(XmlNode xmlPropertyNode, Boolean isStatic)
 at Microsoft.Crm.ObjectModel.CustomControlParameterValidationHelper.ValidateParameters(XmlNode containerNode, ExecutionContext context)
 at Microsoft.Crm.ObjectModel.CustomControlParameterValidationHelper.ValidateCustomControl(XmlNode customControlNode, Int32 entityTypeCode, ExecutionContext executionContext)
 at Microsoft.Crm.ObjectModel.CustomControlParameterValidationHelper.Validate(XmlNode controlDescriptionNode, Int32 entityTypeCode, ExecutionContext executionContext)
 at Microsoft.Crm.ObjectModel.CustomControlNodeValidationStep.Execute(FormValidationContext validationContext)
 at Microsoft.Crm.ObjectModel.FormValidator.Validate(FormValidationContext validationContext)
 at Microsoft.Crm.ObjectModel.SystemFormService.Update(IBusinessEntity entity, ExecutionContext context, DynamicMetadataCache cache, Boolean ignoreFormXmlLabels)
 at Microsoft.Crm.ObjectModel.SystemFormService.Update(IBusinessEntity entity, ExecutionContext context)
 --- End of inner exception stack trace ---
 at Microsoft.Crm.Extensibility.VersionedPluginProxyStepBase.Execute(PipelineExecutionContext context)
 at Microsoft.Crm.Extensibility.PipelineInstrumentationHelper.Execute(Boolean instrumentationEnabled, String stopwatchName, ExecuteWithInstrumentation action, PipelineExecutionContext context)
 at Microsoft.Crm.Extensibility.Pipeline.&lt;&gt;c__DisplayClass2_1.&lt;Execute&gt;b__0()</d2p1:value>
 </KeyValuePairOfstringanyType>
 <KeyValuePairOfstringanyType>
 <d2p1:key>ApiStepKey</d2p1:key>
 <d2p1:value xmlns:d4p1="http://www.w3.org/2001/XMLSchema" i:type="d4p1:string">57066171-5620-4448-aebf-472b99862006</d2p1:value>
 </KeyValuePairOfstringanyType>
 <KeyValuePairOfstringanyType>
 <d2p1:key>ApiDepthKey</d2p1:key>
 <d2p1:value xmlns:d4p1="http://www.w3.org/2001/XMLSchema" i:type="d4p1:string">1</d2p1:value>
 </KeyValuePairOfstringanyType>
 <KeyValuePairOfstringanyType>
 <d2p1:key>ApiActivityIdKey</d2p1:key>
 <d2p1:value xmlns:d4p1="http://www.w3.org/2001/XMLSchema" i:type="d4p1:string">ae3236d6-f4ae-4960-9e58-43739af29027</d2p1:value>
 </KeyValuePairOfstringanyType>
 <KeyValuePairOfstringanyType>
 <d2p1:key>ApiPluginSolutionNameKey</d2p1:key>
 <d2p1:value xmlns:d4p1="http://www.w3.org/2001/XMLSchema" i:type="d4p1:string">System</d2p1:value>
 </KeyValuePairOfstringanyType>
 <KeyValuePairOfstringanyType>
 <d2p1:key>ApiStepSolutionNameKey</d2p1:key>
 <d2p1:value xmlns:d4p1="http://www.w3.org/2001/XMLSchema" i:type="d4p1:string">System</d2p1:value>
 </KeyValuePairOfstringanyType>
 </ErrorDetails>
 <Message>The type attribute is missing from the declaration of Property Output</Message>
 <Timestamp>2019-05-01T09:55:31.5163291Z</Timestamp>
 <ExceptionRetriable>false</ExceptionRetriable>
 <ExceptionSource i:nil="true" />
 <InnerFault i:nil="true" />
 <OriginalException i:nil="true" />
 <TraceText i:nil="true" />
</OrganizationServiceFault>

The manifest:

<?xml version="1.0" encoding="utf-8" ?>
<manifest>
 <control namespace="MyNamespace" constructor="DemoControl" version="0.0.1" display-name-key="DemoControl_Display_Key" description-key="DemoControl_Desc_Key" control-type="standard">
 <!-- property node identifies a specific, configurable piece of data that the control expects from CDS -->
 <property name="Bound" display-name-key="Bound" description-key="Bound" of-type="SingleLine.Text" usage="bound" required="true"/>
 <property name="Bound2" display-name-key="Bound2" description-key="Bound2" of-type="SingleLine.Text" usage="bound" required="true"/>
 <property name="Input" display-name-key="Input" description-key="Input" of-type="SingleLine.Text" usage="input" required="true"/>
 <property name="Output" display-name-key="Output" description-key="Output" of-type="SingleLine.Text" usage="output" required="true"/>
 <resources>
 <code path="index.ts" order="1"/>
 </resources>
 </control>
</manifest>