Use Dynamics WebAPI to get LogicalName or ObjectTypeCode for Entity

If you need to get the LogicalName or ObjectTypeCode of an entity in your Dynamics environment you can utilize the WebAPI to get the metadata.

If you have the LogicalName of the entity you can use this url.
Format:
<Dynamics Url>/api/data/v<Version>/EntityDefinitions(LogicalName='<LogicalName>')?$select=ObjectTypeCode

Example:
https://org12345.crm.dynamics.com/api/data/v9.0/EntityDefinitions(LogicalName='account')?$select=ObjectTypeCode

Data Returned:
{"@odata.context":"https://org6744e6cd.crm.dynamics.com/api/data/v9.0/$metadata#EntityDefinitions(ObjectTypeCode)/$entity","ObjectTypeCode":1,"MetadataId":"70816501-edb9-4740-a16c-6a5efbc05d84"}

If you have the ObjectTypeCode of the entity you can use this url.

Format:
<Dynamics Url>/api/data/v<Version>/EntityDefinitions?$filter=ObjectTypeCode eq <ObjectTypeCode>&$select=LogicalName

Example:
https://org12345.crm.dynamics.com/api/data/v9.0/EntityDefinitions?$filter=ObjectTypeCode eq 1&$select=LogicalName

Data Returned:
{"@odata.context":"https://org6744e6cd.crm.dynamics.com/api/data/v9.0/$metadata#EntityDefinitions(LogicalName)","value":[{"LogicalName":"account","MetadataId":"70816501-edb9-4740-a16c-6a5efbc05d84"}]}