Retrieve Field security for form fields using web api

I have given field permission (READ:NO,WRITE:NO,UPDATE:NO) for a field and for a particular user role. But when i retrieve the records using web api it returns IsValidForCreate,IsValidForUpdate,IsValidForWrtie treurn "TRUE" for all.

{"@odata.context":""@odata.type":"#Microsoft.Dynamics.CRM.IntegerAttributeMetadata","Format":"None","MaxValue":2147483647,"MinValue":-2147483648,"FormulaDefinition":"","SourceTypeMask":0,"AttributeOf":null,"AttributeType":"Integer","ColumnNumber":10317,"DeprecatedVersion":null,"IntroducedVersion":"1.0","EntityLogicalName":"incident","IsCustomAttribute":true,"IsPrimaryId":false,"IsPrimaryName":false,"">xxx/.../$metadataIsValidForCreate":true,"IsValidForRead":true,"IsValidForUpdate":true,"CanBeSecuredForRead":true,"CanBeSecuredForCreate":true,"CanBeSecuredForUpdate":true,"IsSecured":true,"IsRetrievable":false,"IsFilterable":false,"IsSearchable":false,"IsManaged":false,"LinkedAttributeId":null,"LogicalName":"new_massivecase","IsValidForForm":true,"IsRequiredForForm":false,"IsValidForGrid":true,"SchemaName":"new_massivecase","ExternalName":null,"IsLogical":false,"IsDataSourceSecret":false,"InheritsFrom":null,"SourceType":0,"AutoNumberFormat":null,"MetadataId":"bd06d050-509d-e911-a988-000d3a363879","HasChanged":null,"AttributeTypeName":{"Value":"IntegerType"},"Description":{"LocalizedLabels":[{"Label":"","LanguageCode":1033,"IsManaged":false,"MetadataId":"bf06d050-509d-e911-a988-000d3a363879","HasChanged":null}],"UserLocalizedLabel":{"Label":"","LanguageCode":1033,"IsManaged":false,"MetadataId":"xxxxxxxx","HasChanged":null}},"DisplayName":{"LocalizedLabels":[{"Label":"massive case","LanguageCode":1033,"IsManaged":false,"MetadataId":"xxxxxx","HasChanged":null}],"UserLocalizedLabel":{"Label":"massive case","LanguageCode":1033,"IsManaged":false,"MetadataId":"xxxxxx","HasChanged":null}},"IsAuditEnabled":{"Value":true,"CanBeChanged":true,"ManagedPropertyLogicalName":"canmodifyauditsettings"},"IsGlobalFilterEnabled":{"Value":false,"CanBeChanged":true,"ManagedPropertyLogicalName":"canmodifyglobalfiltersettings"},"IsSortableEnabled":{"Value":false,"CanBeChanged":true,"ManagedPropertyLogicalName":"canmodifyissortablesettings"},"IsCustomizable":{"Value":true,"CanBeChanged":true,"ManagedPropertyLogicalName":"iscustomizable"},"IsRenameable":{"Value":true,"CanBeChanged":true,"ManagedPropertyLogicalName":"isrenameable"},"IsValidForAdvancedFind":{"Value":true,"CanBeChanged":true,"ManagedPropertyLogicalName":"canmodifysearchsettings"},"RequiredLevel":{"Value":"None","CanBeChanged":true,"ManagedPropertyLogicalName":"canmodifyrequirementlevelsettings"},"CanModifyAdditionalSettings":{"Value":true,"CanBeChanged":true,"ManagedPropertyLogicalName":"canmodifyadditionalsettings"}}

Kindly let us know what is the reason behind this?